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6 Data Types

This chapter presents data types that are recognized by Oracle and available for use within SQL.

This chapter includes the following sections:

Overview of Data Types

A data type is a classification of a particular type of information or data. Each value manipulated by Oracle has a data type. The data type of a value associates a fixed set of properties with the value. These properties cause Oracle to treat values of one data type differently from values of another.

The data types recognized by Oracle are:

ANSI-supported data types

{ CHARACTER [VARYING] (size)
| { CHAR | NCHAR } VARYING (size)
| VARCHAR (size)
| NATIONAL { CHARACTER | CHAR }
     [VARYING] (size)
| { NUMERIC | DECIMAL | DEC }
     [ (precision [, scale ]) ]
| { INTEGER | INT | SMALLINT }
| FLOAT [ (size) ]
| DOUBLE PRECISION
| REAL
}

Oracle built-in data types

{ character_datatypes
| number_datatypes
| long_and_raw_datatypes
| datetime_datatypes
| large_object_datatypes
| rowid_datatypes
}

Oracle-supplied data types

{ any_types
| XML_types
| spatial_types
| media_types
}

User-defined data types

User-defined data types use Oracle built-in data types and other user-defined data types to model the structure and behavior of data in applications.

See Also:

Oracle Database SQL Language Reference for more information about data types

Oracle Built-In Data Types

This section describes the kinds of Oracle built-in data types.

character_datatypes

{ CHAR [ (size [ BYTE | CHAR ]) ]
| VARCHAR2 (size [ BYTE | CHAR ])
| NCHAR [ (size) ]
| NVARCHAR2 (size)
}

datetime_datatypes

{ DATE
| TIMESTAMP [ (fractional_seconds_precision) ]
     [ WITH [ LOCAL ] TIME ZONE ]
| INTERVAL YEAR [ (year_precision) ] TO MONTH
| INTERVAL DAY [ (day_precision) ] TO SECOND
     [ (fractional_seconds_precision) ]
}

large_object_datatypes

{ BLOB | CLOB | NCLOB | BFILE }

long_and_raw_datatypes

{ LONG | LONG RAW | RAW (size) }

number_datatypes

{ NUMBER [ (precision [, scale ]) ]
| FLOAT [ (precision) ]
| BINARY_FLOAT
| BINARY_DOUBLE
}

rowid_datatypes

{ ROWID | UROWID [ (size) ] }

The codes listed for the data types are used internally by Oracle Database. The data type code of a column or object attribute is returned by the DUMP function.

Table 6-1 Built-in Data Type Summary

Code Data Type Description

1

VARCHAR2(size [BYTE | CHAR])

Variable-length character string having maximum length size bytes or characters. You must specify size for VARCHAR2. Minimum size is 1 byte or 1 character. Maximum size is:

  • 32767 bytes or characters if MAX_STRING_SIZE = EXTENDED

  • 4000 bytes or characters if MAX_STRING_SIZE = STANDARD

Refer to Oracle Database SQL Language Reference for more information on the MAX_STRING_SIZE initialization parameter.

BYTE indicates that the column will have byte length semantics. CHAR indicates that the column will have character semantics.

1

NVARCHAR2(size)

Variable-length Unicode character string having maximum length size characters. You must specify size for NVARCHAR2. The number of bytes can be up to two times size for AL16UTF16 encoding and three times size for UTF8 encoding. Maximum size is determined by the national character set definition, with an upper limit of:

  • 32767 bytes if MAX_STRING_SIZE = EXTENDED

  • 4000 bytes if MAX_STRING_SIZE = STANDARD

Refer to Oracle Database SQL Language Reference for more information on the MAX_STRING_SIZE initialization parameter.

2

NUMBER [ (p [, s]) ]

Number having precision p and scale s. The precision p can range from 1 to 38. The scale s can range from -84 to 127. Both precision and scale are in decimal digits. A NUMBER value requires from 1 to 22 bytes.

2

FLOAT [(p)]

A subtype of the NUMBER data type having precision p. A FLOAT value is represented internally as NUMBER. The precision p can range from 1 to 126 binary digits. A FLOAT value requires from 1 to 22 bytes.

8

LONG

Character data of variable length up to 2 gigabytes, or 231 -1 bytes. Provided for backward compatibility.

12

DATE

Valid date range from January 1, 4712 BC, to December 31, 9999 AD. The default format is determined explicitly by the NLS_DATE_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is fixed at 7 bytes. This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It does not have fractional seconds or a time zone.

100

BINARY_FLOAT

32-bit floating point number. This data type requires 4 bytes.

101

BINARY_DOUBLE

64-bit floating point number. This data type requires 8 bytes.

180

TIMESTAMP [(fractional_seconds_precision)]

Year, month, and day values of date, as well as hour, minute, and second values of time, where fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values of fractional_seconds_precision are 0 to 9. The default is 6. The default format is determined explicitly by the NLS_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is 7 or 11 bytes, depending on the precision. This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It contains fractional seconds but does not have a time zone.

181

TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE

All values of TIMESTAMP as well as time zone displacement value, where 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. The default format is determined explicitly by the NLS_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is fixed at 13 bytes. This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, TIMEZONE_HOUR, and TIMEZONE_MINUTE. It has fractional seconds and an explicit time zone.

231

TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE

All values of TIMESTAMP WITH TIME ZONE, with the following exceptions:

  • Data is normalized to the database time zone when it is stored in the database.

  • When the data is retrieved, users see the data in the session time zone.

The default format is determined explicitly by the NLS_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is 7 or 11 bytes, depending on the precision.

182

INTERVAL YEAR [(year_precision)] TO MONTH

Stores a period of time in years and months, where year_precision is the number of digits in the YEAR datetime field. Accepted values are 0 to 9. The default is 2. The size is fixed at 5 bytes.

183

INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)]

Stores a period of time in days, hours, minutes, and seconds, where

  • day_precision is the maximum number of digits in the DAY datetime field. 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 field. Accepted values are 0 to 9. The default is 6.

The size is fixed at 11 bytes.

23

RAW(size)

Raw binary data of length size bytes. You must specify size for a RAW value. Maximum size is:

  • 32767 bytes if MAX_STRING_SIZE = EXTENDED

  • 2000 bytes if MAX_STRING_SIZE = STANDARD

Refer to Oracle Database SQL Language Reference for more information on the MAX_STRING_SIZE initialization parameter.

24

LONG RAW

Raw binary data of variable length up to 2 gigabytes.

69

ROWID

Base 64 string representing the unique address of a row in its table. This data type is primarily for values returned by the ROWID pseudocolumn.

208

UROWID [(size)]

Base 64 string representing the logical address of a row of an index-organized table. The optional size is the size of a column of type UROWID. The maximum size and default is 4000 bytes.

96

CHAR [(size [BYTE | CHAR])]

Fixed-length character data of length size bytes or characters. Maximum size is 2000 bytes or characters. Default and minimum size is 1 byte.

BYTE and CHAR have the same semantics as for VARCHAR2.

96

NCHAR[(size)]

Fixed-length character data of length size characters. The number of bytes can be up to two times size for AL16UTF16 encoding and three times size for UTF8 encoding. Maximum size is determined by the national character set definition, with an upper limit of 2000 bytes. Default and minimum size is 1 character.

112

CLOB

A character large object containing single-byte or multibyte characters. Both fixed-width and variable-width character sets are supported, both using the database character set. Maximum size is (4 gigabytes - 1) * (database block size).

112

NCLOB

A character large object containing Unicode characters. Both fixed-width and variable-width character sets are supported, both using the database national character set. Maximum size is (4 gigabytes - 1) * (database block size). Stores national character set data.

113

BLOB

A binary large object. Maximum size is (4 gigabytes - 1) * (database block size).

114

BFILE

Contains a locator to a large binary file stored outside the database. Enables byte stream I/O access to external LOBs residing on the database server. Maximum size is 4 gigabytes.

See Also:

Oracle Database SQL Language Reference for more information about built-in data types

Oracle-Supplied Data Types

This section shows the syntax for the Oracle-supplied data types.

any_types 

{ SYS.AnyData | SYS.AnyType | SYS.AnyDataSet }

spatial_types 

{ SDO_Geometry | SDO_Topo_Geometry |SDO_GeoRaster }

XML_types 

{ XMLType | URIType }

Converting to Oracle Data Types

SQL statements that create tables and clusters can also use ANSI data types and data types from the IBM products SQL/DS and DB2. Oracle recognizes the ANSI or IBM data type name that differs from the Oracle data type name, records it as the name of the data type of the column, and then stores the column data in an Oracle data type based on the conversions shown in the following table.

Table 6-2 ANSI Data Types Converted to Oracle Data Types

ANSI SQL Data Type Oracle Data Type

CHARACTER(n)

CHAR(n)

CHAR(n)

CHARACTER VARYING(n)

CHAR VARYING(n)

VARCHAR2(n)

NATIONAL CHARACTER(n)

NATIONAL CHAR(n)

NCHAR(n)

NCHAR(n)

NATIONAL CHARACTER VARYING(n)

NATIONAL CHAR VARYING(n)

NCHAR VARYING(n)

NVARCHAR2(n)

NUMERIC[(p,s)]

DECIMAL[(p,s)] (Note 1)

NUMBER(p,s)

INTEGER

INT

SMALLINT

NUMBER(38)

FLOAT (Note 2)

DOUBLE PRECISION (Note 3)

REAL (Note 4)

FLOAT(126)

FLOAT(126)

FLOAT(63)

Notes:

  1. The NUMERIC and DECIMAL data types can specify only fixed-point numbers. For those data types, the scale (s) defaults to 0.

  2. The FLOAT data type is a floating-point number with a binary precision b. The default precision for this data type is 126 binary, or 38 decimal.

  3. The DOUBLE PRECISION data type is a floating-point number with binary precision 126.

  4. The REAL data type is a floating-point number with a binary precision of 63, or 18 decimal.

Do not define columns with the following SQL/DS and DB2 data types, because they have no corresponding Oracle data type:

  • GRAPHIC

  • LONG VARGRAPHIC

  • VARGRAPHIC

  • TIME

Note that data of type TIME can also be expressed as Oracle datetime data.

See Also:

Oracle Database SQL Language Reference for more information on data types