This chapter provides a reference to Oracle external datatypes used by OCI applications. It also discusses Oracle datatypes and the conversions between internal and external representations that occur when you transfer data between your program and Oracle.
This chapter contains these topics:
See Also:
For detailed information about Oracle internal datatypes, see the Oracle Database SQL ReferenceOne of the main functions of an OCI program is to communicate with a database through an Oracle server. The OCI application may retrieve data from database tables through SQL SELECT
queries, or it may modify existing data in tables through INSERT
, UPDATE
, or DELETE
statements.
Inside a database, values are stored in columns in tables. Internally, Oracle represents data in particular formats known as internal datatypes. Examples of internal datatypes include NUMBER
, CHAR
, and DATE
.
In general, OCI applications do not work with internal datatype representations of data, but with host language datatypes which are predefined by the language in which they are written. When data is transferred between an OCI client application and a database table, the OCI libraries convert the data between internal datatypes and external datatypes.
External datatypes are host language types that have been defined in the OCI header files. When an OCI application binds input variables, one of the bind parameters is an indication of the external datatype code (or SQLT code) of the variable. Similarly, when output variables are specified in a define call, the external representation of the retrieved data must be specified.
In some cases, external datatypes are similar to internal types. External types provide a convenience for the programmer by making it possible to work with host language types instead of proprietary data formats.
Note:
Even though some external types are similar to internal types, an OCI application never binds to internal datatypes. They are discussed here because it can be useful to understand how internal types can map to external types.The OCI is capable of performing a wide range of datatype conversions when transferring data between Oracle and an OCI application. There are more OCI external datatypes than Oracle internal datatypes. In some cases a single external type maps to an internal type; in other cases multiple external types map to an single internal type.
The many-to-one mappings for some datatypes provide flexibility for the OCI programmer. For example, if you are processing the SQL statement
SELECT sal FROM emp WHERE empno = :employee_number
and you want the salary to be returned as character data, instead of a binary floating-point format, specify an Oracle external string datatype, such as VARCHAR2
(code = 1) or CHAR
(code = 96) for the dty
parameter in the OCIDefineByPos()
call for the sal
column. You also need to declare a string variable in your program and specify its address in the valuep
parameter.
If you want the salary information to be returned as a binary floating-point value, however, specify the FLOAT
(code = 4) external datatype. You also need to define a variable of the appropriate type for the valuep
parameter.
Oracle performs most data conversions transparently. The ability to specify almost any external datatype provides a lot of power for performing specialized tasks. For example, you can input and output DATE
values in pure binary format, with no character conversion involved, by using the DATE
external datatype. See the description of the DATE external datatype for more information.
To control data conversion, you must use the appropriate external datatype codes in the bind and define routines. You must tell Oracle where the input or output variables are in your OCI program and their datatypes and lengths.
OCI also supports an additional set of OCI typecodes which are used by Oracle's type management system to represent datatypes of object type attributes. There is a set of predefined constants which can be used to represent these typecodes. The constants each contain the prefix OCI_TYPECODE
.
In summary, the OCI programmer must be aware of the following different datatypes or data representations:
Internal Oracle datatypes, which are used by table columns in an Oracle database. These also include datatypes used by PL/SQL which are not used by Oracle columns (for example, indexed table, boolean, record).
See Also:
"Internal Datatypes"External OCI datatypes, which are used to specify host language representations of Oracle data.
OCI_TYPECODE
values, which are used to Oracle to represent type information for object type attributes.
Information about a column's internal datatype is conveyed to your application in the form of an internal datatype code. Once your application knows what type of data will be returned, it can make appropriate decisions about how to convert and format the output data. The Oracle internal datatype codes are listed in the section "Internal Datatypes".
See Also:
For detailed information about Oracle internal datatypes, see the Oracle Database SQL Reference.
For information about describing select-list items in a query, see the section "Describing Select-list Items".
An external datatype code indicates to Oracle how a host variable represents data in your program. This determines how the data is converted when returned to output variables in your program, or how it is converted from input (bind) variables to Oracle column values. For example, if you want to convert a NUMBER
in an Oracle column to a variable-length character array, you specify the VARCHAR2 external datatype code in the OCIDefineByPos()
call that defines the output variable.
To convert a bind variable to a value in an Oracle column, specify the external datatype code that corresponds to the type of the bind variable. For example, if you want to input a character string such as 02-FEB-65 to a DATE
column, specify the datatype as a character string and set the length parameter to nine.
It is always the programmer's responsibility to make sure that values are convertible. If you try to insert the string "
MY BIRTHDAY"
into a DATE
column, you will get an error when you execute the statement.
See Also:
For a complete list of the external datatypes and datatype codes, see Table 3-2, "External Datatypes and Codes"Table 3-1 lists the Oracle internal (also known as built-in) datatypes, along with each type's maximum internal length and datatype code.
Table 3-1 Internal Oracle Datatypes
See Also:
For more information about these built-in datatypes, see the Oracle Database SQL Reference.You can use the piecewise capabilities provided by OCIBindByName()
, OCIBindByPos()
, OCIDefineByPos()
, OCIStmtGetPieceInfo()
and OCIStmtSetPieceInfo()
to perform inserts, updates or fetches involving column data of these types.
You can use five Oracle internal datatypes to specify columns that contain characters or arrays of bytes: CHAR
, VARCHAR2
, RAW
, LONG
, and LONG
RAW
.
Note:
LOBs can contain characters andBFILE
s can contain binary data. They are handled differently than other types, so they are not included in this discussion. See Chapter 7, "LOB and BFILE Operations", for more information about these datatypes.CHAR
, VARCHAR2
, and LONG
columns normally hold character data. RAW
and LONG
RAW
hold bytes that are not interpreted as characters, for example, pixel values in a bit-mapped graphic image. Character data can be transformed when passed through a gateway between networks. Character data passed between machines using different languages, where single characters may be represented by differing numbers of bytes, can be significantly changed in length. Raw data is never converted in this way.
It is the responsibility of the database designer to choose the appropriate Oracle internal datatype for each column in the table. The OCI programmer must be aware of the many possible ways that character and byte-array data can be represented and converted between variables in the OCI program and Oracle tables.
When an array holds characters, the length parameter for the array in an OCI call is always passed in and returned in bytes, not characters.
The Universal ROWID
(UROWID
) is a datatype that can store both logical and physical rowids of Oracle tables. Logical rowids are primary key-based logical identifiers for the rows of Index-Organized Tables (IOTs).
To use columns of the UROWID
datatype, the value of the COMPATIBLE
initialization parameter must be set to 8.1 or higher.
The following host variables can be bound to Universal ROWIDs:
SQLT_CHR
(VARCHAR2
)
SQLT_VCS
(VARCHAR
)
SQLT_STR
(NULL
-terminated string)
SQLT_LVC
(LONG VARCHAR
)
SLQT_AFC
(CHAR
)
SQLT_AVC
(CHARZ
)
SQLT_VST
(OCI String)
SQLT_RDD
(ROWID
descriptor)
The BINARY_FLOAT
and BINARY_DOUBLE
datatypes represent single-precision and double-precision floating point values that mostly conform to the IEEE754 standard for Floating Point Arithmetic.
Prior to the addition of these datatypes, all numeric values in an Oracle database were stored in the Oracle NUMBER
format. These new binary floating point types will not replace Oracle NUMBER
. Rather, they are alternatives to Oracle NUMBER
that provide the advantage of using less disk storage.
These internal types are represented by the following codes:
All the following host variables can be bound to BINARY_FLOAT
and BINARY_DOUBLE
datatypes:
SQLT_BFLOAT
(native float)
SQLT_BDOUBLE
(native double)
SQLT_INT
(integer)
SQLT_FLT
(float)
SQLT_NUM
(Oracle NUMBER
)
SQLT_UIN
(unsigned)
SQLT_VNU
(VARNUM
)
SQLT_CHR
(VARCHAR2
)
SQLT_VCS
(VARCHAR
)
SQLT_STR
(NULL
-terminated String)
SQLT_LVC
(LONG
VARCHAR
)
SQLT_AFC
(CHAR
)
SQLT_AVC
(CHARZ
)
SQLT_VST
(OCIString)
For best performance, you are advised to use external types SQLT_BFLOAT
and SQLT_BDOUBLE
in conjunction with the BINARY_FLOAT
and BINARY_DOUBLE
datatypes.
Table 3-2 lists datatype codes for external datatypes. For each datatype, the table lists the program variable types for C from or to which Oracle internal data is normally converted.
Table 3-2 External Datatypes and Codes
EXTERNAL DATATYPE | CODE | PROGRAM VARIABLE | OCI DEFINED CONSTANT |
---|---|---|---|
|
1 |
char[n] |
|
|
2 |
unsigned char[21] |
|
8-bit signed |
3 |
signed char |
|
16-bit signed |
3 |
signed short, signed int |
|
32-bit signed |
3 |
signed int, signed long |
|
|
4 |
float, double |
|
|
5 |
char[n+1] |
|
|
6 |
char[22] |
|
|
8 |
char[n] |
|
|
9 |
char[n+sizeof(short integer)] |
|
|
12 |
char[7] |
|
|
15 |
unsigned char[n+sizeof(short integer)] |
|
native float |
21 |
float |
|
native double |
22 |
double |
|
|
23 |
unsigned char[n] |
|
|
24 |
unsigned char[n] |
|
|
68 |
unsigned |
|
|
94 |
char[n+sizeof(integer)] |
|
|
95 |
unsigned char[n+sizeof(integer)] |
|
|
96 |
char[n] |
|
|
97 |
char[n+1] |
|
|
104 |
OCIRowid * |
|
NAMED DATATYPE |
108 |
struct |
|
|
110 |
OCIRef |
|
Character LOB descriptor |
112 |
OCILobLocator (see note 2) |
|
Binary LOB descriptor |
113 |
OCILobLocator (see note 2) |
|
Binary FILE descriptor |
114 |
OCILobLocator |
|
|
155 |
OCIString |
|
|
156 |
OCIDate * |
|
|
184 |
OCIDateTime * |
|
|
187 |
OCIDateTime * |
|
|
188 |
OCIDateTime * |
|
|
189 |
OCIInterval * |
|
|
190 |
OCIInterval * |
|
|
232 |
OCIDateTime * |
|
Note:
Where the length is shown as n, it is a variable, and depends on the requirements of the program (or of the operating system in the case ofROWID
).
For more information on the use of these datatypes, refer to Chapter 11, "Object-Relational Datatypes in OCI".
In applications using datatype mappings generated by OTT, CLOBs may be mapped as OCIClobLocator, and BLOBs may be mapped as OCIBlobLocator. For more information, refer to Chapter 14, "Using the Object Type Translator with OCI".
The following three types are internal to PL/SQL and cannot be returned as values by OCI:
Boolean, SQLT_BOL
Indexed Table, SQLT_TAB
Record, SQLT_REC
The VARCHAR2
datatype is a variable-length string of characters with a maximum length of 4000 bytes.
Note:
If you are using Oracle objects, you can work with a specialOCIString
external datatype using a set of predefined OCI functions. Refer to Chapter 11, "Object-Relational Datatypes in OCI" for more information about this datatype.The value_sz
parameter determines the length in the OCIBindByName()
or OCIBindByPos()
call.
If the value_sz
parameter is greater than zero, Oracle obtains the bind variable value by reading exactly that many bytes, starting at the buffer address in your program. Trailing blanks are stripped, and the resulting value is used in the SQL statement or PL/SQL block. If, in the case of an INSERT
statement, the resulting value is longer than the defined length of the database column, the INSERT
fails, and an error is returned.
Note:
A trailingNULL
is not stripped. Variables should be blank-padded but not NULL
-terminated.If the value_sz
parameter is zero, Oracle treats the bind variable as a NULL
, regardless of its actual content. Of course, a NULL
must be allowed for the bind variable value in the SQL statement. If you try to insert a NULL
into a column that has a NOT
NULL
integrity constraint, Oracle issues an error, and the row is not inserted.
When the Oracle internal (column) datatype is NUMBER
, input from a character string that contains the character representation of a number is legal. Input character strings are converted to internal numeric format. If the VARCHAR2
string contains an illegal conversion character, Oracle returns an error and the value is not inserted into the database.
Specify the desired length for the return value in the value_sz
parameter of the OCIDefineByPos()
call, or the value_sz
parameter of OCIBindByName()
or OCIBindByPos()
for PL/SQL blocks. If zero is specified for the length, no data is returned.
If you omit the rlenp
parameter of OCIDefineByPos()
, returned values are blank-padded to the buffer length, and NULL
s are returned as a string of blank characters. If rlenp
is included, returned values are not blank-padded. Instead, their actual lengths are returned in the rlenp
parameter.
To check if a NULL
is returned or if character truncation has occurred, include an indicator parameter in the OCIDefineByPos()
call. Oracle sets the indicator parameter to -1 when a NULL
is fetched and to the original column length when the returned value is truncated. Otherwise, it is set to zero. If you do not specify an indicator parameter and a NULL
is selected, the fetch call returns the error code OCI_SUCCESS_WITH_INFO
. Retrieving diagnostic information on the error will return ORA-1405.
See Also:
"Indicator Variables"You should not need to use NUMBER
as an external datatype. If you do use it, Oracle returns numeric values in its internal 21-byte binary format and will expect this format on input. The following discussion is included for completeness only.
Note:
If you are using objects in an Oracle database server, you can work with a specialOCINumber
datatype using a set of predefined OCI functions. Refer to Chapter 11, "Object-Relational Datatypes in OCI" for more information about this datatype.Oracle stores values of the NUMBER
datatype in a variable-length format. The first byte is the exponent and is followed by 1 to 20 mantissa bytes. The high-order bit of the exponent byte is the sign bit; it is set for positive numbers and it is cleared for negative numbers. The lower 7 bits represent the exponent, which is a base-100 digit with an offset of 65.
To calculate the decimal exponent, add 65 to the base-100 exponent and add another 128 if the number is positive. If the number is negative, you do the same, but subsequently the bits are inverted. For example, -5 has a base-100 exponent = 62 (0x3e). The decimal exponent is thus (~0x3e) -128 - 65 = 0xc1 -128 -65 = 193 -128 -65 = 0.
Each mantissa byte is a base-100 digit, in the range 1..100. For positive numbers, the digit has 1 added to it. So, the mantissa digit for the value 5 is 6. For negative numbers, instead of adding 1, the digit is subtracted from 101. So, the mantissa digit for the number -5 is 96 (101 - 5). Negative numbers have a byte containing 102 appended to the data bytes. However, negative numbers that have 20 mantissa bytes do not have the trailing 102 byte. Because the mantissa digits are stored in base 100, each byte can represent 2 decimal digits. The mantissa is normalized; leading zeroes are not stored.
Up to 20 data bytes can represent the mantissa. However, only 19 are guaranteed to be accurate. The 19 data bytes, each representing a base-100 digit, yield a maximum precision of 38 digits for an Oracle NUMBER
.
If you specify the datatype code 2 in the dty
parameter of an OCIDefineByPos()
call, your program receives numeric data in this Oracle internal format. The output variable should be a 21-byte array to accommodate the largest possible number. Note that only the bytes that represent the number are returned. There is no blank padding or NULL
termination. If you need to know the number of bytes returned, use the VARNUM
external datatype instead of NUMBER
.
See Also:
"VARNUM" for a description of the internal NUMBER format
The INTEGER
datatype converts numbers. An external integer is a signed binary number; the size in bytes is system dependent. The host system architecture determines the order of the bytes in the variable. A length specification is required for input and output. If the number being returned from Oracle is not an integer, the fractional part is discarded, and no error or other indication is returned. If the number to be returned exceeds the capacity of a signed integer for the system, Oracle returns an "overflow on conversion" error.
The FLOAT
datatype processes numbers that have fractional parts or that exceed the capacity of an integer. The number is represented in the host system's floating-point format. Normally the length is either four or eight bytes. The length specification is required for both input and output.
The internal format of an Oracle number is decimal, and most floating-point implementations are binary; therefore Oracle can represent numbers with greater precision than floating-point representations.
Note:
You may receive a round-off error when converting betweenFLOAT
and NUMBER
. Using a FLOAT
as a bind variable in a query may return an ORA-1403 error. You can avoid this situation by converting the FLOAT
into a STRING
and then using VARCHAR2
or a NULL
-terminated string for the operation.The NULL
-terminated STRING
format behaves like the VARCHAR2 format, except that the string must contain a NULL
terminator character. This datatype is most useful for C language programs.
The string length supplied in the OCIBindByName()
or OCIBindByPos()
call limits the scan for the NULL
terminator. If the NULL
terminator is not found within the length specified, Oracle issues the error
ORA-01480: trailing NULL
missing from STR
bind value
If the length is not specified in the bind call, the OCI uses an implied maximum string length of 4000.
The minimum string length is two bytes. If the first character is a NULL
terminator and the length is specified as two, a NULL
is inserted in the column, if permitted. Unlike types VARCHAR2
and CHAR
, a string containing all blanks is not treated as a NULL
on input; it is inserted as is.
Note:
Unlike earlier versions of the OCI, in release 8.0 or later, you cannot pass -1 for the string length parameter of aNULL
-terminated stringA NULL
terminator is placed after the last character returned. If the string exceeds the field length specified, it is truncated and the last character position of the output variable contains the NULL
terminator.
A NULL
select-list item returns a NULL
terminator character in the first character position. An ORA-01405 error is possible, as well.
The VARNUM
datatype is like the external NUMBER
datatype, except that the first byte contains the length of the number representation. This length does not include the length byte itself. Reserve 22 bytes to receive the longest possible VARNUM
. Set the length byte when you send a VARNUM
value to Oracle Database.
Table 3-3 shows several examples of the VARNUM
values returned for numbers in a table.
The LONG
datatype stores character strings longer than 4000 bytes. You can store up to two gigabytes (2^31-1 bytes) in a LONG
column. Columns of this type are used only for storage and retrieval of long strings. They cannot be used in functions, expressions, or WHERE
clauses. LONG
column values are generally converted to and from character strings.
Do not create tables with LONG
columns. Use LOB
columns (CLOB
, NCLOB
, or BLOB
) instead. LONG
columns are supported only for backward compatibility.
Oracle also recommends that you convert existing LONG
columns to LOB
columns. LOB
columns are subject to far fewer restrictions than LONG
columns. Furthermore, LOB
functionality is enhanced in every release, but LONG
functionality has been static for several releases.
The VARCHAR
datatype stores character strings of varying length. The first two bytes contain the length of the character string, and the remaining bytes contain the string. The specified length of the string in a bind or a define call must include the two length bytes, so the largest VARCHAR
string that can be received or sent is 65533 bytes long, not 65535.
The DATE
datatype can update, insert, or retrieve a date value using the Oracle internal date binary format. A date in binary format contains seven bytes, as shown in Table 3-4.
Table 3-4 Format of the DATE Datatype
Byte | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
---|---|---|---|---|---|---|---|
Meaning |
Century |
Year |
Month |
Day |
Hour |
Minute |
Second |
Example (for 30-NOV-1992, 3:17 PM) |
119 |
192 |
11 |
30 |
16 |
18 |
1 |
The century and year bytes (bytes 1 and 2) are in excess-100 notation. The first byte stores the value of the year, which is 1992, as an integer, divided by 100, giving 119 in excess-100 notation. The second byte stores year modulo 100, giving 192. Dates Before Common Era (BCE) are less than 100. The era begins on 01-JAN-4712 BCE, which is Julian day 1. For this date, the century byte is 53, and the year byte is 88. The hour, minute, and second bytes are in excess-1 notation. The hour byte ranges from 1 to 24, the minute and second bytes from 1 to 60. If no time was specified when the date was created, the time defaults to midnight (1, 1, 1).
When you enter a date in binary format using the DATE
external datatype, the database does not do consistency or range checking. All data in this format must be carefully validated before input.
Note:
There is little need to use the Oracle externalDATE
datatype in ordinary database operations. It is much more convenient to convert DATE
into character format, because the program usually deals with data in a character format, such as DD-MON-YY.When a DATE
column is converted to a character string in your program, it is returned using the default format mask for your session, or as specified in the INIT.ORA
file.
See Also:
If you are using objects in an Oracle database, you can work with a specialOCIDate
datatype using a set of predefined OCI functions.
Refer to Chapter 11, "Object-Relational Datatypes in OCI" for more information about this datatype.
For information about DATETIME
and INTERVAL
datatypes, refer to "Datetime and Interval Datatype Descriptors".
The RAW
datatype is used for binary data or byte strings that are not to be interpreted by Oracle, for example, to store graphics character sequences. The maximum length of a RAW
column is 2000 bytes.
See Also:
Oracle Database SQL Reference.When RAW
data in an Oracle table is converted to a character string in a program, the data is represented in hexadecimal character code. Each byte of the RAW
data is returned as two characters that indicate the value of the byte, from '00' to 'FF'. If you want to input a character string in your program to a RAW
column in an Oracle table, you must code the data in the character string using this hexadecimal code.
You can use the piecewise capabilities provided by OCIDefineByPos()
, OCIBindByName()
, OCIBindByPos()
, OCIStmtGetPieceInfo()
, and OCIStmtSetPieceInfo()
to perform inserts, updates, or fetches involving RAW
(or LONG
RAW
) columns.
See Also:
If you are using objects in an Oracle database, you can work with a specialOCIRaw
datatype using a set of predefined OCI functions. Refer to Chapter 11, "Object-Relational Datatypes in OCI" for more information about this datatype.The VARRAW
datatype is similar to the RAW
datatype. However, the first two bytes contain the length of the data. The specified length of the string in a bind or a define call must include the two length bytes, so the largest VARRAW
string that can be received or sent is 65533 bytes, not 65535. For converting longer strings, use the LONG
VARRAW
external datatype.
The LONG
RAW
datatype is similar to the RAW
datatype, except that it stores raw data with a length up to two gigabytes (2^31-1 bytes).
The UNSIGNED
datatype is used for unsigned binary integers. The size in bytes is system dependent. The host system architecture determines the order of the bytes in a word. A length specification is required for input and output. If the number being output from Oracle is not an integer, the fractional part is discarded, and no error or other indication is returned. If the number to be returned exceeds the capacity of an unsigned integer for the system, Oracle returns an "overflow on conversion" error.
The LONG
VARCHAR
datatype stores data from and into an Oracle LONG
column. The first four bytes of a LONG
VARCHAR
contain the length of the item. So, the maximum length of a stored item is 2^31-5 bytes.
The LONG
VARRAW
datatype is used to store data from and into an Oracle LONG
RAW
column. The length is contained in the first four bytes. The maximum length is 2^31-5 bytes.
The CHAR
datatype is a string of characters, with a maximum length of 2000. CHAR
strings are compared using blank-padded comparison semantics.
See Also:
Oracle Database SQL ReferenceThe length is determined by the value_sz
parameter in the OCIBindByName()
or OCIBindByPos()
call.
Note:
The entire contents of the buffer (value_sz
chars) is passed to the database, including any trailing blanks or NULL
sIf the value_sz
parameter is zero, Oracle treats the bind variable as a NULL
, regardless of its actual content. Of course, a NULL
must be allowed for the bind variable value in the SQL statement. If you try to insert a NULL
into a column that has a NOT
NULL
integrity constraint, Oracle issues an error and does not insert the row.
Negative values for the value_sz
parameter are not allowed for CHARs.
When the Oracle internal (column) datatype is NUMBER
, input from a character string that contains the character representation of a number is legal. Input character strings are converted to internal numeric format. If the CHAR
string contains an illegal conversion character, Oracle returns an error and does not insert the value. Number conversion follows the conventions established by Globalization Support settings for your system. For example, your system might be configured to recognize a comma (,) rather than a period (.) as the decimal point.
Specify the desired length for the return value in the value_sz
parameter of the OCIDefineByPos()
call. If zero is specified for the length, no data is returned.
If you omit the rlenp
parameter of OCIDefineByPos()
, returned values are blank padded to the buffer length, and NULL
s are returned as a string of blank characters. If rlenp
is included, returned values are not blank padded. Instead, their actual lengths are returned in the rlenp
parameter.
To check whether a NULL
is returned or if character truncation has occurred, include an indicator parameter or array of indicator parameters in the OCIDefineByPos()
call. An indicator parameter is set to -1 when a NULL
is fetched and to the original column length when the returned value is truncated. Otherwise, it is set to zero. If you do not specify an indicator parameter and a NULL
is selected, the fetch call returns an ORA-01405 error.
See Also:
"Indicator Variables"You can also request output to a character string from an internal NUMBER
datatype. Number conversion follows the conventions established by the Globalization Support settings for your system. For example, your system might use a comma (,) rather than a period (.) as the decimal point.
The CHARZ
external datatype is similar to the CHAR
datatype, except that the string must be NULL
-terminated on input, and Oracle places a NULL
-terminator character at the end of the string on output. The NULL
terminator serves only to delimit the string on input or output; it is not part of the data in the table.
On input, the length parameter must indicate the exact length, including the NULL
terminator. For example, if an array in C is declared as
char my_num[] = "123.45";
then the length parameter when you bind my_num
must be seven. Any other value would return an error for this example.
The following new external datatypes were introduced with or after release 8.0. These datatypes are not supported when you connect to an Oracle release 7 server.
Note:
Both internal and external datatypes have Oracle-defined constant values, such asSQLT_NTY
, SQLT_REF
, corresponding to their datatype codes. Although the constants are not listed for all of the types in this chapter, they are used in this section when discussing new Oracle datatypes. The datatype constants are also used in other chapters of this guide when referring to these new types.Named datatypes are user-defined types which are specified with the CREATE
TYPE
command in SQL. Examples include object types, varrays, and nested tables. In the OCI, named datatype refers to a host language representation of the type. The SQLT_NTY
datatype code is used when binding or defining named datatypes.
In a C application, named datatypes are represented as C structs. These structs can be generated from types stored in the database by using the Object Type Translator. These types correspond to OCI_TYPECODE_OBJECT
.
See Also:
For more information about working with named datatypes in the OCI, see Chapter 11, "Object-Relational Datatypes in OCI".
For information about how named datatypes are represented as C structs, refer to Chapter 14, "Using the Object Type Translator with OCI".
This is a reference to a named datatype. The C language representation of a REF
is a variable declared to be of type OCIRef *
. The SQLT_REF
datatype code is used when binding or defining REFs.
Access to REFs is only possible when an OCI application has been initialized in object mode. When REFs are retrieved from the server, they are stored in the client-side object cache.
To allocate a REF
for use in your application, you should declare a variable to be a pointer to a REF
, and then call OCIObjectNew()
, passing OCI_TYPECODE_REF
as the typecode
parameter.
See Also:
For more information about working with REFs in the OCI, see Chapter 13, "Object Advanced Topics in OCI"The ROWID
datatype identifies a particular row in a database table. ROWID
can be a select-list item in a query, such as:
SELECT ROWID, ename, empno FROM emp
In this case, you can use the returned ROWID
in further DELETE
statements.
If you are performing a SELECT
for UPDATE
, the ROWID
is implicitly returned. This ROWID
can be read into a user-allocated ROWID
descriptor using OCIAttrGet()
on the statement handle and used in a subsequent UPDATE
statement. The prefetch operation fetches all ROWIDs
on a SELECT
for UPDATE
; use prefetching and then a single row fetch.
You access rowids through the use of a ROWID
descriptor, which you can use as a bind or define variable.
See Also:
"OCI Descriptors" and "Positioned Updates and Deletes" for more information about the use of theROWID
descriptorA LOB (Large Object) stores binary or character data up to 128 terabytes in length. Binary data is stored in a BLOB
(Binary LOB), and character data is stored in a CLOB
(Character LOB) or NCLOB
(National Character LOB).
LOB values may or may not be stored inline with other row data in the database. In either case, LOBs have the full transactional support of the database server. A database table stores a LOB locator that points to the LOB value, which may be in a different storage space.
When an OCI application issues a SQL query which includes a LOB column or attribute in its select-list, fetching the result(s) of the query returns the locator, rather than the actual LOB value. In OCI, the LOB locator maps to a variable of type OCILobLocator
.
Note:
Depending on your application, you may or may not want to use LOB locators. You can use the data interface for LOBs, which does not require LOB locators. In this interface, you can bind or define character data forCLOB
columns or RAW
data for BLOB
columns.See Also:
For more information about descriptors, including the LOB locator, see the section "OCI Descriptors"
For more information about LOBs refer to the Oracle Database SQL Reference and the Oracle Database Application Developer's Guide - Large Objects.
The OCI functions for LOBs take a LOB locator as one of their arguments. The OCI functions assume that the locator has already been created, whether or not the LOB to which it points contains data.
Bind and define operations are performed on the LOB locator, which is allocated with the OCIDescriptorAlloc()
function.
The locator is always fetched first using SQL or OCIObjectPin()
, and then operations are performed using the locator. The OCI functions never take the actual LOB value as a parameter.
See Also:
For more information about OCI LOB functions, see Chapter 7, "LOB and BFILE Operations"The datatype codes available for binding or defining LOBs are:
SQLT_BLOB
- a binary LOB datatype.
SQLT_CLOB
- a character LOB datatype.
The NCLOB
is a special type of CLOB
with the following requirements:
To write into or read from an NCLOB
, the user must set the character set form (csfrm
) parameter to be SQLCS_NCHAR.
The amount (amtp
) parameter in calls involving CLOB
s and NCLOB
s is always interpreted in terms of characters, rather than bytes, for fixed-width character sets.
See Also:
"LOB and BFILE Functions in OCI"Oracle supports access to binary files, or BFILE
s. The BFILE
datatype provides access to LOBs that are stored in file systems outside an Oracle database.
A BFILE
column or attribute stores a file LOB locator, which serves as a pointer to a binary file on the server's file system. The locator maintains the directory object and the filename. The maximum size of a BFILE
is the smaller of the operating system maximum file size or UB8MAXVAL
.
Binary file LOBs do not participate in transactions. Rather, the underlying operating system provides file integrity and durability.
The database administrator must ensure that the file exists and that Oracle processes have operating system read permissions on the file.
The BFILE
datatype allows read-only support of large binary files; you cannot modify a file through Oracle. Oracle provides APIs to access file data.
The datatype code available for binding or defining BFILE
s is:
SQLT_BFILE
- a binary FILE LOB datatype
See Also:
For more information about directory aliases, refer to the Oracle Database Application Developer's Guide - Large ObjectsThe BLOB
datatype stores unstructured binary large objects. BLOB
s can be thought of as bit streams with no character set semantics. BLOB
s can store up to 128 terabytes of binary data.
BLOB
s have full transactional support; changes made through the OCI participate fully in the transaction. The BLOB
value manipulations can be committed or rolled back. You cannot save a BLOB
locator in a variable in one transaction and then use it in another transaction or session.
The CLOB
datatype stores fixed- or variable-width character data. CLOB
s can store up to 128 terabytes of character data.
CLOB
s have full transactional support; changes made through the OCI participate fully in the transaction. The CLOB
value manipulations can be committed or rolled back. You cannot save a CLOB
locator in a variable in one transaction and then use it in another transaction or session.
An NCLOB
is a national character version of a CLOB
. It stores fixed-width, single-byte or multibyte national character set (NCHAR
) data, or variable-width character set data. NCLOB
s can store up to 128 terabytes of character text data.
NCLOB
s have full transactional support; changes made through the OCI participate fully in the transaction. NCLOB
value manipulations can be committed or rolled back. You cannot save a NCLOB
locator in a variable in one transaction and then use it in another transaction or session.
The datetime and interval datatype descriptors are briefly summarized here.
See Also:
Oracle Database SQL ReferenceThe ANSI
DATE
is based on the DATE
, but contains no time portion. It also has no time zone. ANSI
DATE
follows the ANSI
specification for the DATE
datatype. When assigning an ANSI
DATE
to a DATE
or a timestamp datatype, the time portion of the Oracle DATE
and the timestamp are set to zero. When assigning a DATE
or a timestamp to an ANSI
DATE
, the time portion is ignored.
You are encouraged to instead use the TIMESTAMP
datatype which contains both date and time.
The TIMESTAMP
datatype is an extension of the DATE
datatype. It stores the year, month, and day of the DATE
datatype, plus the hour, minute, and second values. It has no time zone. The TIMESTAMP
datatype has the form:
TIMESTAMP(fractional_seconds_precision)
where the optional fractional_seconds_precision
specifies the number of digits in the fractional part of the SECOND
datetime field and can be a number in the range 0 to 9. The default is 6.
TIMESTAMP
WITH
TIME
ZONE
(TSTZ
) is a variant of TIMESTAMP
that includes an explicit time zone displacement in its value. The time zone displacement is the difference in hours and minutes between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). The TIMESTAMP
WITH
TIME
ZONE
datatype has the form:
TIMESTAMP(fractional_seconds_precision) WITH TIME ZONE
where fractional_seconds_precision
optionally specifies the number of digits in the fractional part of the SECOND
datetime field, and can be a number in the range 0 to 9. The default is 6.
Two TIMESTAMP
WITH
TIME
ZONE
values are considered identical if they represent the same instant in UTC, regardless of the TIME
ZONE
offsets stored in the data.
TIMESTAMP
WITH
LOCAL
TIME
ZONE
(TSLTZ
) is another variant of TIMESTAMP
that includes a time zone displacement in its value. Storage is in the same format as for TIMESTAMP
. This type differs from TIMESTAMP
WITH
TIME
ZONE
in that data stored in the database is normalized to the database time zone, and the time zone displacement is not stored as part of the column data. When retrieving the data, Oracle returns it in your local session time zone.
The time zone displacement is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). The TIMESTAMP
WITH
LOCAL
TIME
ZONE
datatype has the form:
TIMESTAMP(fractional_seconds_precision) WITH LOCAL TIME ZONE
where fractional_seconds_precision
optionally specifies the number of digits in the fractional part of the SECOND
datetime field and can be a number in the range 0 to 9. The default is 6.
INTERVAL
YEAR
TO
MONTH
stores a period of time using the YEAR
and MONTH
datetime fields. The INTERVAL
YEAR
TO
MONTH
datatype has the form:
INTERVAL YEAR(year_precision) TO MONTH
where the optional year_precision
is the number of digits in the YEAR
datetime field. The default value of year_precision
is 2.
INTERVAL
DAY
TO
SECOND
stores a period of time in terms of days, hours, minutes, and seconds. The INTERVAL
DAY
TO
SECOND
datatype has the form:
INTERVAL DAY (day_precision) TO SECOND(fractional_seconds_precision)
where:
day_precision
is the optional number of digits in the DAY
datetime field. It is optional. Accepted values are 0 to 9. The default is 2.
fractional_seconds_precision
is the number of digits in the fractional part of the SECOND
datetime field. Accepted values are 0 to 9. The default is 6.
Note:
To avoid unexpected results in your DML operations on datetime data, you can verify the database and session time zones by querying the built-in SQL functionsDBTIMEZONE
and SESSIONTIMEZONE
. If the time zones have not been set manually, Oracle uses the operating system time zone by default. If the operating system time zone is not a valid Oracle time zone, Oracle uses UTC as the default value.The native float (SQLT_BFLOAT
) and native double (SQLT_BDOUBLE
) datatypes represent the single-precision and double-precision floating point values. They are represented natively, that is, in the host system's floating point format.
Note that these new external types were added to externally represent the BINARY_FLOAT
and BINARY_DOUBLE
internal datatypes. Thus, performance for the new internal types will be best when used in conjunction with external types native float and native double respectively. This draws a clear distinction between the existing representation of floating point values (SQLT_FLT
) and these new types.
OCI supports Oracle-defined C datatypes for mapping user-defined datatypes to C representations (for example, OCINumber
, OCIArray
). OCI provides a set of calls to operate on these datatypes, and to use these datatypes in bind and define operations, in conjunction with OCI external datatypes.
See Also:
For information on using these Oracle-defined C datatypes, refer to Chapter 11, "Object-Relational Datatypes in OCI"Table 3-5 show the supported conversions from internal datatypes to external datatypes, and from external datatypes into internal column representations, for all datatypes available through release 7.3. Information about data conversions for datatypes newer than release 7.3 is listed here:
REFs stored in the database are converted to SQLT_REF
on output.
SQLT_REF
is converted to the internal representation of REFs on input.
Named datatypes stored in the database can be converted to SQLT_NTY
(and represented by a C struct in the application) on output.
SQLT_NTY
(represented by a C struct in an application) is converted to the internal representation of the corresponding type on input.
LOBs are shown in Table 3-6, because of the width limitation.
See Also:
For information aboutOCIString
, OCINumber
, and other new datatypes, refer to Chapter 11, "Object-Relational Datatypes in OCI"- | INTERNAL DATATYPES-> | - | - | - | - | - | - | - | - |
---|---|---|---|---|---|---|---|---|---|
EXTERNALDATATYPES | VARCHAR2 | NUMBER | LONG | ROWID | UROWID | DATE | RAW | LONG RAW | CHAR |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I/O(3) |
- |
|
I/O(4) |
I/O |
I |
- |
- |
- |
- |
- |
I/O(4) |
|
I/O(4) |
I/O |
I |
- |
- |
- |
- |
- |
I/O(4) |
|
I/O(4) |
I/O |
I |
- |
- |
- |
- |
- |
I/O(4) |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I/O(3, 5) |
I/O |
|
I/O(4) |
I/O |
I |
- |
- |
- |
- |
- |
I/O(4) |
|
I/O(4) |
I/O |
I |
- |
- |
- |
- |
- |
I/O(4) |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I/O(3, 5) |
I/O |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I/O(3, 5) |
I/O |
|
I/O |
- |
I |
- |
- |
I/O |
- |
- |
I/O |
|
I/O(6) |
- |
I(5, 6) |
- |
- |
- |
I/O |
I/O |
I/O(6) |
|
I/O(6) |
- |
I(5, 6) |
- |
- |
- |
I/O |
I/O |
I/O(6) |
|
O(6) |
- |
I(5, 6) |
- |
- |
- |
I/O |
I/O |
O(6) |
|
I/O(4) |
I/O |
I |
- |
- |
- |
- |
- |
I/O(4) |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I/O(3, 5) |
I/O |
|
I/O(6) |
- |
I(5, 6) |
- |
- |
- |
I/O |
I/O |
I/O(6) |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I(3) |
I/O |
|
I/O |
I/O |
I/O |
I/O(1) |
I/O(1) |
I/O(2) |
I/O(3) |
I(3) |
I/O |
|
I(1) |
- |
- |
I/O |
I/O |
- |
- |
- |
I(1) |
Legend:
I = Conversion valid for input only
O = Conversion valid for output only
I/O = Conversion valid for input or output
Notes:
(1) For input, host string must be in Oracle ROWID/UROWID
format.
On output, column value is returned in Oracle ROWID/UROWID
format.
(2) For input, host string must be in the Oracle DATE
character format.
On output, column value is returned in Oracle DATE
format.
(3) For input, host string must be in hex format.
On output, column value is returned in hex format.
(4) For output, column value must represent a valid number.
(5) Length must be less than or equal to 2000.
(6) On input, column value is stored in hex format.
On output, column value must be in hex format.
You can also use one of the character datatypes for the host variable used in a fetch or insert operation from or to a datetime or interval column. Oracle will do the conversion between the character datatype and datetime/interval datatype for you.
Table 3-7 Data Conversion for Datetime and Interval Types
External Types/Internal Types | VARCHAR,CHAR | DATE | TS | TSTZ | TSLTZ | INTERVAL YEAR TO MONTH | INTERVAL DAY TO SECOND |
---|---|---|---|---|---|---|---|
|
I/O |
I/O |
I/O |
I/O |
I/O |
I/O |
I/O |
|
I/O |
I/O |
I/O |
I/O |
I/O |
- |
- |
|
I/O |
I/O |
I/O |
I/O |
I/O |
- |
- |
|
I/O |
I/O |
I/O |
I/O |
I/O |
- |
- |
|
I/O |
I/O |
I/O |
I/O |
I/O |
- |
- |
|
I/O |
I/O |
I/O |
I/O |
I/O |
- |
- |
|
I/O |
I/O |
I/O |
I/O |
I/O |
- |
- |
|
I/O |
- |
- |
- |
- |
I/O |
- |
|
I/O |
- |
- |
- |
- |
- |
I/O |
When assigning a source with time zone to a target without a time zone, the time zone portion of the source is ignored. On assigning a source without a time zone to a target with a time zone, the time zone of the target is set to the session's default time zone
When assigning an Oracle DATE
to a TIMESTAMP
, the TIME
portion of the DATE
is copied over to the TIMESTAMP
. When assigning a TIMESTAMP
to Oracle DATE
, the TIME
portion of the result DATE
is set to zero. This is done to encourage upgrading of Oracle DATE
to ANSI
compliant DATETIME
datatypes
When assigning an ANSI
DATE
to an Oracle DATE
or a TIMESTAMP
, the TIME
portion of the Oracle DATE
and the TIMESTAMP
are set to zero. When assigning an Oracle DATE
or a TIMESTAMP
to an ANSI DATE
, the TIME
portion is ignored
When assigning a DATETIME
to a character string, the DATETIME
is converted using the session's default DATETIME
format. When assigning a character string to a DATETIME
, the string must contain a valid DATETIME
value based on the session's default DATETIME
format
When assigning a character string to an INTERVAL
, the character string must be a valid INTERVAL
character format.
(1) When converting from TSLTZ to CHAR, DATE, TIMESTAMP, and TSTZ, the value will be adjusted to the session time zone.
(2) When converting from CHAR
, DATE
, and TIMESTAMP
to TSLTZ
, the session time zone will be stored in memory.
(3) When assigning TSLTZ
to ANSI
DATE
, the time portion will be zero.
(4) When converting from TSTZ
, the time zone which the time stamp is in will be stored in memory.
(5) When assigning a character string to an interval, the character string must be a valid interval character format.
OCI has full forward and backward compatibility between a client application and the database server as far as the datetime and date columns are concerned.
The only datetime datatype available to a pre-9.0 application is the DATE
datatype, SQLT_DAT
. When a pre-9.0 client that defined a buffer as SQLT_DAT
, tries to obtain data from a TSLTZ
column, then only the date portion of the value will be returned to the client.
In this case the new client can have a bind or define buffer of type SQLT_TIMESTAMP_LTZ
. The following compatibilities are maintained in this case.
If any client application tries to insert a SQLT_TIMESTAMP_LTZ
(or any of the new datetime datatypes) into a DATE
column, an error will be issued since there is potential data loss in this situation.
When a client has an OUT bind or a define buffer that is of datatype SQLT_TIMESTAMP_LTZ
and the underlying server side SQL buffer or column is of DATE
type, then the session time zone is assigned.
Table 3-8 shows the supported conversions between internal numerical datatypes and all relevant external types. An (I) implies that the conversion is valid for input only (binds), and (O) implies that the conversion is valid for output only (defines), while an (I/O) implies that the conversion is valid for input as well as output (binds and defines).
Table 3-8 Data Conversion for External Datatypes to Internal Numerical Datatypes
External Types/Internal Types | BINARY_FLOAT | BINARY_DOUBLE |
---|---|---|
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
|
I/O |
I/O |
Table 3-9 shows the supported conversions between all relevant internal types and numerical external types. An (I) implies that the conversion is valid for input only (only for binds), and (O) implies that the conversion is valid for output only (only for defines), while an (I/O) implies that the conversion is valid for input as well as output (binds and defines).
There is a unique typecode associated with each Oracle type, whether scalar, collection, reference, or object type. This typecode identifies the type, and is used by Oracle to manage information about object type attributes. This typecode system is designed to be generic and extensible, and is not tied to a direct one-to-one mapping to Oracle datatypes. Consider the following SQL statements:
CREATE TYPE my_type AS OBJECT ( attr1 NUMBER, attr2 INTEGER, attr3 SMALLINT); CREATE TABLE my_table AS TABLE OF my_type;
These statements create an object type and an object table. When it is created, my_table
will have three columns, all of which are of Oracle NUMBER
type, because SMALLINT
and INTEGER
map internally to NUMBER
. The internal representation of the attributes of my_type
, however, maintains the distinction between the datatypes of the three attributes: attr1
is OCI_TYPECODE_NUMBER
, attr2
is OCI_TYPECODE_INTEGER
, and attr3
is OCI_TYPECODE_SMALLINT
. If an application describes my_type
, these typecodes are returned.
OCITypeCode
is the C datatype of the typecode. The typecode is used by some OCI functions, like OCIObjectNew()
, where it helps determine what type of object is created. It is also returned as the value of some attributes when an object is described; for example, querying the OCI_ATTR_TYPECODE
attribute of a type returns an OCITypeCode
value.
Table 3-10 lists the possible values for an OCITypeCode
. There is a value corresponding to each Oracle datatype.
Table 3-10 OCITypeCode Values and Datatypes
Value | Datatype |
---|---|
|
REF |
|
DATE |
|
TIMESTAMP |
|
TIMESTAMP WITH TIME ZONE |
|
TIMESTAMP WITH LOCAL TIME ZONE |
|
INTERVAL YEAR TO MONTH |
|
INTERVAL DAY TO SECOND |
|
single-precision real |
|
double-precision real |
|
floating-point |
|
Oracle NUMBER |
|
BINARY_FLOAT |
|
BINARY_DOUBLE |
|
decimal |
|
octet |
|
integer |
|
small int |
|
RAW |
|
variable string ANSI SQL, that is, VARCHAR2 |
|
variable string Oracle SQL, that is, VARCHAR |
|
fixed-length string inside SQL, that is SQL CHAR |
|
variable-length array (varray) |
|
multiset |
|
character large object (CLOB) |
|
binary large object (BLOB) |
|
binary large object file ( |
|
named object type, or SYS.XMLType |
|
Domain (named primitive type) |
Oracle recognizes two different sets of datatype code values. One set is distinguished by the SQLT_
prefix, the other by the OCI_TYPECODE_
prefix.
The SQLT
typecodes are used by OCI to specify a datatype in a bind or define operation, enabling you to control data conversions between Oracle and OCI client applications. The OCI_TYPECODE
types are used by Oracle's type system to reference or describe predefined types when manipulating or creating user-defined types.
In many cases there are direct mappings between SQLT
and OCI_TYPECODE
values. In other cases, however, there is not a direct one-to-one mapping. For example OCI_TYPECODE_SIGNED16
, OCI_TYPECODE_SIGNED32
, OCI_TYPECODE_INTEGER
, OCI_TYPECODE_OCTET
, and OCI_TYPECODE_SMALLINT
are all mapped to the SQLT_INT
type.
Table 3-11 illustrates the mappings between SQLT
and OCI_TYPECODE
types.
Table 3-11 OCI_TYPECODE to SQLT Mappings
Oracle Type System Typename | Oracle Type System Type | Equivalent SQLT Type |
---|---|---|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<NONE> |
|
|
|
|
|
|
|
|
|
OBJECT or |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<NONE> |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<NONE> |
|
|
|
|
|
|
Notes:
1. n is the size of the string in bytes
2. These are floating point numbers, the precision is given in terms of binary digits. b is the precision of the number in binary digits.
3. This is equivalent to a NUMBER
with no decimal places.
4. i is the size of the number in bytes, set as part of an OCI call.
5. p is the precision of the number in decimal digits; s is the scale of the number in decimal digits.
6. Can only be part of a named collection type.
Throughout this guide you will see references to datatypes like ub2
or sb4
, or to constants like UB4MAXVAL
. These types are defined in the oratypes.h
header file, which is found in the public
directory. The exact contents may vary according to the operating system you are using.
Note:
The use of the datatypes inoratypes.h
is the only supported means of supplying parameters to the OCI.