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Oracle® Database JDBC Developer's Guide,
11g Release 2 (11.2)

Part Number E16548-02
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11 Accessing and Manipulating Oracle Data

This chapter describes data access in oracle.sql.* formats, as opposed to standard Java formats. Using oracle.sql.* formats involves casting your result sets and statements to OracleResultSet, OracleStatement, OraclePreparedStatement, and OracleCallableStatement, as appropriate, and using the getOracleObject, setOracleObject, getXXX, and setXXX methods of these classes, where XXX corresponds to the types in the oracle.sql package.

This chapter covers the following topics:

Data Type Mappings

The Oracle JDBC drivers support standard JDBC types as well as Oracle-specific data types. This section documents standard and Oracle-specific SQL-Java default type mappings. This section contains the following topics:

Table of Mappings

Table 11-1 shows the default mappings between SQL data types, JDBC type codes, standard Java types, and Oracle extended types.

The SQL Data Types column lists the SQL types that exist in Oracle Database 11g. The JDBC Type Codes column lists data type codes supported by the JDBC standard and defined in the java.sql.Types class or by Oracle in the oracle.jdbc.OracleTypes class. For standard type codes, the codes are identical in these two classes.

The Standard Java Types column lists standard types defined in the Java language. The Oracle Extension Java Types column lists the oracle.sql.* Java types that correspond to each SQL data type in the database. These are Oracle extensions that let you retrieve all SQL data in the form of a oracle.sql.* Java type.

Note:

In general, the Oracle JDBC drivers are optimized to manipulate SQL data using the standard JDBC types. In a few specialized cases, it may be advantageous to use the Oracle extension classes that are available in the oracle.sql package. But, Oracle strongly recommends to use the standard JDBC types instead of Oracle extensions, whenever possible. For more information about when to use Oracle extension, refer to "Standard Types Versus Oracle Types".

See Also:

"Package oracle.sql" for more information on Oracle extensions

Table 11-1 Default Mappings Between SQL Types and Java Types

SQL Data Types JDBC Type Codes Standard Java Types Oracle Extension Java Types
 

STANDARD JDBC TYPES:

   

CHAR

java.sql.Types.CHAR

java.lang.String

oracle.sql.CHAR

VARCHAR2

java.sql.Types.VARCHAR

java.lang.String

oracle.sql.CHAR

LONG

java.sql.Types.LONGVARCHAR

java.lang.String

oracle.sql.CHAR

NUMBER

java.sql.Types.NUMERIC

java.math.BigDecimal

oracle.sql.NUMBER

NUMBER

java.sql.Types.DECIMAL

java.math.BigDecimal

oracle.sql.NUMBER

NUMBER

java.sql.Types.BIT

boolean

oracle.sql.NUMBER

NUMBER

java.sql.Types.TINYINT

byte

oracle.sql.NUMBER

NUMBER

java.sql.Types.SMALLINT

short

oracle.sql.NUMBER

NUMBER

java.sql.Types.INTEGER

int

oracle.sql.NUMBER

NUMBER

java.sql.Types.BIGINT

long

oracle.sql.NUMBER

NUMBER

java.sql.Types.REAL

float

oracle.sql.NUMBER

NUMBER

java.sql.Types.FLOAT

double

oracle.sql.NUMBER

NUMBER

java.sql.Types.DOUBLE

double

oracle.sql.NUMBER

RAW

java.sql.Types.BINARY

byte[]

oracle.sql.RAW

RAW

java.sql.Types.VARBINARY

byte[]

oracle.sql.RAW

LONGRAW

java.sql.Types.LONGVARBINARY

byte[]

oracle.sql.RAW

DATE

java.sql.Types.DATE

java.sql.Date

oracle.sql.DATE

DATE

java.sql.Types.TIME

java.sql.Time

oracle.sql.DATE

TIMESTAMP

java.sql.Types.TIMESTAMP

javal.sql.Timestamp

oracle.sql.TIMESTAMP

BLOB

java.sql.Types.BLOB

java.sql.Blob

oracle.sql.BLOB

CLOB

java.sql.Types.CLOB

java.sql.Clob

oracle.sql.CLOB

user-defined object

java.sql.Types.STRUCT

java.sql.Struct

oracle.sql.STRUCT

user-defined reference

java.sql.Types.REF

java.sql.Ref

oracle.sql.REF

user-defined collection

java.sql.Types.ARRAY

java.sql.Array

oracle.sql.ARRAY

ROWID

java.sql.Types.ROWID

java.sql.RowId

oracle.sql.ROWID

NCLOB

java.sql.Types.NCLOB

java.sql.NClob

oracle.sql.NCLOB

NCHAR

java.sql.Types.NCHAR

java.lang.String

oracle.sql.CHAR

 

ORACLE EXTENSIONS:

   

BFILE

oracle.jdbc.OracleTypes.BFILE

NA

oracle.sql.BFILE

REF CURSOR

oracle.jdbc.OracleTypes.CURSOR

java.sql.ResultSet

oracle.jdbc.OracleResultSet

TIMESTAMP

oracle.jdbc.OracleTypes.TIMESTAMP

java.sql.Timestamp

oracle.sql.TIMESTAMP

TIMESTAMP WITH TIME ZONE

oracle.jdbc.OracleTypes.TIMESTAMPTZ

java.sql.Timestamp

oracle.sql.TIMESTAMPTZ

TIMESTAMP WITH LOCAL TIME ZONE

oracle.jdbc.OracleTypes.TIMESTAMPLTZ

java.sql.Timestamp

oracle.sql.TIMESTAMPLTZ


Note:

For database versions, such as 8.1.7, which do not support the TIMESTAMP data type, TIMESTAMP is mapped to DATE.

Notes Regarding Mappings

This section provides further detail regarding mappings for NUMBER and user-defined types.

NUMBER Types

For the different type codes that an Oracle NUMBER value can correspond to, call the getter routine that is appropriate for the size of the data for mapping to work properly. For example, call getByte to get a Java tinyint value for an item x, where -128 < x < 128.

User-Defined Types

User-defined types, such as objects, object references, and collections, map by default to weak Java types, such as java.sql.Struct, but alternatively can map to strongly typed custom Java classes. Custom Java classes can implement one of two interfaces:

  • The standard java.sql.SQLData

  • The Oracle-specific oracle.sql.ORAData

Data Conversion Considerations

When JDBC programs retrieve SQL data into Java, you can use standard Java types, or you can use types of the oracle.sql package. This section covers the following topics:

Standard Types Versus Oracle Types

The Oracle data types in oracle.sql store data in the same bit format as used by the database. In versions of the Oracle JDBC drivers prior to Oracle Database 10g, the Oracle data types were generally more efficient. The Oracle Database 10g JDBC drivers were substantially updated. As a result, in most cases the standard Java types are preferred to the data types in oracle.sql.*. In particular, java.lang.String is much more efficient than oracle.sql.CHAR.

In general, Oracle recommends that you use the Java standard types. The exceptions to this are:

  • Use the oracle.sql.OraData rather than the java.sql.SqlData if the OraData functionality better suits your needs.

  • Use oracle.sql.NUMBER rather than java.lang.Double if you need to retain the exact values of floating point numbers. Oracle NUMBER is a decimal representation and Java Double and Float are binary representations. Conversion from one format to the other can result in slight variations in the actual value represented. Additionally, the range of values that can be represented using the two formats is different.

    Use oracle.sql.NUMBER rather than java.math.BigDecimal when performance is critical and you are not manipulating the values, just reading and writing them.

  • Use oracle.sql.DATE or oracle.sql.TIMESTAMP rather than java.sql.Date or java.sql.Timestamp if you are using a JDK version earlier than JDK 1.6 or require maximum performance. You can also use the oracle.sql data type if you want to read many date values, and compute or display only a small percentage.

    Note:

    Due to a bug in all versions of Java prior to JDK 1.6, construction of java.lang.Date and java.lang.Timestamp objects is slow, especially in multithreaded environments. This bug is fixed in JDK 1.6.
  • Use oracle.sql.CHAR only when you have data from some external source, which has been represented in an Oracle character set encoding. In all other cases, you should use java.lang.String.

  • STRUCT, ARRAY, BLOB, CLOB, REF, and ROWID are all the implementation classes of the corresponding JDBC standard interface types. So, there is no benefit of using the Oracle extension types as they are identical to the JDBC standard types.

  • BFILE, TIMESTAMPTZ, and TIMESTAMPLTZ have no representation in the JDBC standard. You must use these Oracle extensions.

  • In all other cases, you should use the standard JDBC type rather than the Oracle extensions.

Note:

If you convert an oracle.sql data type to a Java standard data type, then the benefits of using the oracle.sql data type are lost.

Converting SQL NULL Data

Java represents a SQL NULL datum by the Java value null. Java data types fall into two categories: primitive types, such as byte, int, and float, and object types, such as class instances. The primitive types cannot represent null. Instead, they store null as the value zero, as defined by the JDBC specification. This can lead to ambiguity when you try to interpret your results.

In contrast, Java object types can represent null. The Java language defines an object container type corresponding to every primitive type that can represent null. The object container types must be used as the targets for SQL data to detect SQL NULL without ambiguity.

Testing for NULLs

You cannot use a relational operator to compare NULL values with each other or with other values. For example, the following SELECT statement does not return any row even if the COMM column contains one or more NULL values.

PreparedStatement pstmt = conn.prepareStatement(
  "SELECT * FROM EMP WHERE COMM = ?"); 
pstmt.setNull(1, java.sql.Types.VARCHAR); 

The next example shows how to compare values for equality when some return values might be NULL. The following code returns all the ENAMES from the EMP table that are NULL, if there is no value of 100 for COMM.

PreparedStatement pstmt = conn.prepareStatement("SELECT ENAME FROM EMP 
  WHERE COMM =? OR  ((COMM IS NULL) AND (? IS NULL))"); 
pstmt.setBigDecimal(1, new BigDecimal(100)); 
pstmt.setNull(2, java.sql.Types.VARCHAR); 

Result Set and Statement Extensions

The JDBC Statement object returns an OracleResultSet object, typed as a java.sql.ResultSet. If you want to apply only standard JDBC methods to the object, then keep it as a ResultSet type. However, if you want to use the Oracle extensions on the object, then you must cast it to OracleResultSet. All of the Oracle Result Set extensions are in the oracle.jdbc.OracleResultSet interface and all the Statement extensions are in the oracle.jdbc.OracleStatement interface.

For example, assuming you have a standard Statement object stmt, do the following if you want to use only standard JDBC ResultSet methods:

ResultSet rs = stmt.executeQuery("SELECT * FROM emp");

If you need the extended functionality provided by the Oracle extensions to JDBC, you can select the results into a standard ResultSet variable and then cast that variable to OracleResultSet later.

Key extensions to the result set and statement classes include the getOracleObject and setOracleObject methods, used to access and manipulate data in oracle.sql.* formats.

Comparison of Oracle get and set Methods to Standard JDBC

This section describes get and set methods, particularly the JDBC standard getObject and setObject methods and the Oracle-specific getOracleObject and setOracleObject methods, and how to access data in oracle.sql.* format compared with Java format.

Although there are specific getXXX methods for all the Oracle SQL types, you can use the general get methods for convenience or simplicity, or if you are not certain in advance what type of data you will receive.

This section covers the following topics:

Note:

You cannot qualify a column name with a table name and pass it as a parameter to the getXXX method. For example:
ResultSet rset = stmt.executeQuery("SELECT emp.deptno, dept.deptno FROM emp, dept");
rset.getInt("emp.deptno");

The getInt method in the preceding code will throw an exception. To uniquely identify the columns in the getXXX method, you can either use column index or specify column aliases in the query and use these aliases in the getXXX method.

Standard getObject Method

The standard getObject method of a result set or callable statement has a return type of java.lang.Object. The class of the object returned is based on its SQL type, as follows:

  • For SQL data types that are not Oracle-specific, getObject returns the default Java type corresponding to the SQL type of the column, following the mapping in the JDBC specification.

  • For Oracle-specific data types, getObject returns an object of the appropriate oracle.sql.* class, such as oracle.sql.ROWID.

  • For Oracle database objects, getObject returns a Java object of the class specified in your type map. Type maps specify a mapping from database named types to Java classes. The getObject(parameter_index) method uses the default type map of the connection. The getObject(parameter_index, map) enables you to pass in a type map. If the type map does not provide a mapping for a particular Oracle object, then getObject returns an oracle.sql.STRUCT object.

Oracle getOracleObject Method

If you want to retrieve data from a result set or callable statement as an oracle.sql.* object, then you must follow a special process. For a Result Set, you must cast the Result Set itself to oracle.jdbc.OracleResultSet and then call getOracleObject instead of getObject. The same applies to CallableStatement and oracle.jdbc.OracleCallableStatement.

The return type of getOracleObject is oracle.sql.Datum. The actual returned object is an instance of the appropriate oracle.sql.* class. The method signature is:

public oracle.sql.Datum getOracleObject(int parameter_index)

When you retrieve data into a Datum variable, you can use the standard Java instanceof operator to determine which oracle.sql.* type it really is.

Example: Using getOracleObject with a Result Set

The following example creates a table that contains a column of CHAR data and a column containing a BFILE locator. A SELECT statement retrieves the contents of the table as a result set. The getOracleObject then retrieves the CHAR data into the char_datum variable and the BFILE locator into the bfile_datum variable. Note that because getOracleObject returns a Datum object, the return values must be cast to CHAR and BFILE, respectively.

stmt.execute ("CREATE TABLE bfile_table (x VARCHAR2 (30), b BFILE)");
stmt.execute 
    ("INSERT INTO bfile_table VALUES ('one', BFILENAME ('TEST_DIR', 'file1'))");

ResultSet rset = stmt.executeQuery ("SELECT * FROM bfile_table");
while (rset.next ())
{
   CHAR char_datum = (CHAR) ((OracleResultSet)rset).getOracleObject (1);
   BFILE bfile_datum = (BFILE) ((OracleResultSet)rset).getOracleObject (2);
   ...
}

Example: Using getOracleObject in a Callable Statement

The following example prepares a call to the procedure myGetDate, which associates a character string with a date. The program passes "SCOTT" to the prepared call and registers the DATE type as an output parameter. After the call is run, getOracleObject retrieves the date associated with "SCOTT". Note that because getOracleObject returns a Datum object, the results are cast to DATE.

OracleCallableStatement cstmt = (OracleCallableStatement)conn.prepareCall
                                   ("begin myGetDate (?, ?); end;");

cstmt.setString (1, "SCOTT");
cstmt.registerOutParameter (2, Types.DATE);
cstmt.execute ();

DATE date = (DATE) ((OracleCallableStatement)cstmt).getOracleObject (2);
...

Summary of getObject and getOracleObject Return Types

Table 11-2 lists the underlying return types for the getObject and getOracleObject methods for each Oracle SQL type.

Keep in mind the following when you use these methods:

  • getObjectalways returns data into a java.lang.Object instance

  • getOracleObject always returns data into an oracle.sql.Datum instance

You must cast the returned object to use any special functionality.

Table 11-2 getObject and getOracleObject Return Types

Oracle SQL Type getObject Underlying Return Type getOracleObject Underlying Return Type

CHAR

String

oracle.sql.CHAR

VARCHAR2

String

oracle.sql.CHAR

NCHAR

String

oracle.sql.CHAR

LONG

String

oracle.sql.CHAR

NUMBER

java.math.BigDecimal

oracle.sql.NUMBER

RAW

byte[]

oracle.sql.RAW

LONGRAW

byte[]

oracle.sql.RAW

DATE

java.sql.Date

oracle.sql.DATE

TIMESTAMP

java.sql.TimestampFoot 1 

oracle.sql.TIMESTAMP

TIMESTAMP WITH TIME ZONE

oracle.sql.TIMESTAMPTZ

oracle.sql.TIMESTAMPTZ

TIMESTAMP WITH LOCAL TIME ZONE

oracle.sql.TIMESTAMPLTZ

oracle.sql.TIMESTAMPLTZ

BINARY_FLOAT

java.lang.Float

oracle.sql.BINARY_FLOAT

BINARY_DOUBLE

java.lang.Double

oracle.sql.BINARY_DOUBLE

INTERVAL DAY TO SECOND

oracle.sql.INTERVALDS

oracle.sql.INTERVALDS

INTERVAL YEAR TO MONTH

oracle.sql.INTERVALYM

oracle.sql.INTERVALYM

ROWID

oracle.sql.ROWID

oracle.sql.ROWID

REF CURSOR

java.sql.ResultSet

(not supported)

BLOB

oracle.sql.BLOB

oracle.sql.BLOB

CLOB

oracle.sql.CLOB

oracle.sql.CLOB

NCLOB

java.sql.NClob

oracle.sql.NCLOB

BFILE

oracle.sql.BFILE

oracle.sql.BFILE

Oracle object

class specified in type map

or oracle.sql.STRUCT (if no type map entry)

oracle.sql.STRUCT

Oracle object reference

oracle.sql.REF

oracle.sql.REF

collection (varray or nested table)

oracle.sql.ARRAY

oracle.sql.ARRAY


Footnote 1 ResultSet.getObject returns java.sql.Timestamp only if the oracle.jdbc.J2EE13Compliant connection property is set to TRUE, else the method returns oracle.sql.TIMESTAMP.

Note:

The ResultSet.getObject method returns java.sql.Timestamp for the TIMESTAMP SQL type, only when the connection property oracle.jdbc.J2EE13Compliant is set to TRUE. This property has to be set when the connection is obtained. If this connection property is not set or if it is set after the connection is obtained, then the ResultSet.getObject method returns oracle.sql.TIMESTAMP for the TIMESTAMP SQL type.

The oracle.jdbc.J2EE13Compliant connection property can also be set without changing the code in the following ways:

  • Including the ojdbc5dms.jar or ojdbc6dms.jar files in the CLASSPATH. These files set oracle.jdbc.J2EE13Compliant to TRUE by default. These are specific to the Oracle Application Server release and are not available as part of the general JDBC release. They are located in $ORACLE_HOME/jdbc/lib.

  • Setting the system property by calling the java command with the flag -Doracle.jdbc.J2EE13Compliant=true. For example,

    java -Doracle.jdbc.J2EE13Compliant=true ...
    

When the J2EE13Compliant is set to TRUE the action is as in Table B-3 of the JDBC specification.

See Also:

Table A-1, "Valid SQL Data Type-Java Class Mappings", for information about type compatibility between all SQL and Java types.

Other getXXX Methods

Standard JDBC provides a getXXX for each standard Java type, such as getByte, getInt, getFloat, and so on. Each of these returns exactly what the method name implies.

In addition, the OracleResultSet and OracleCallableStatement classes provide a full complement of getXXX methods corresponding to all the oracle.sql.* types. Each getXXX method returns an oracle.sql.XXX object. For example, getROWID returns an oracle.sql.ROWID object.

There is no performance advantage in using the specific getXXX methods. However, they do save you the trouble of casting, because the return type is specific to the object being returned.

This section covers the following topics:

Return Types of getXXX Methods

Refer to the Java doc to know the return types for each getXXX method and also which are Oracle extensions under Java Development Kit (JDK) 1.6. You must cast the returned object to OracleResultSet or OracleCallableStatement to use methods that are Oracle extensions.

Special Notes about getXXX Methods

This section provides additional details about some getXXX methods.

getBigDecimal

JDBC 2.0 simplified method signatures for the getBigDecimal method. The previous input signatures were:

(int columnIndex, int scale) or (String columnName, int scale)

The simplified input signature is:

(int columnIndex) or (String columnName)

The scale parameter, used to specify the number of digits to the right of the decimal, is no longer necessary. The Oracle JDBC drivers retrieve numeric values with full precision.

getBoolean

Because there is no BOOLEAN database type, when you use getBoolean a data type conversion always occurs. The getBoolean method is supported only for numeric columns. When applied to these columns, getBoolean interprets any zero value as false and any other value as true. When applied to any other sort of column, getBoolean raises the exception java.lang.NumberFormatException.

Data Types For Returned Objects from getObject and getXXX

The return type of getObject is java.lang.Object. The returned value is an instance of a subclass of java.lang.Object. Similarly, the return type of getOracleObject is oracle.sql.Datum, and the class of the returned value is a subclass of oracle.sql.Datum. You typically cast the returned object to the appropriate class to use particular methods and functionality of that class.

In addition, you have the option of using a specific getXXX method instead of the generic getObject or getOracleObject methods. The getXXX methods enable you to avoid casting, because the return type of getXXX corresponds to the type of object returned. For example, the return type of getCLOB is oracle.sql.CLOB, as opposed to java.lang.Object.

Example of Casting Return Values

This example assumes that you have fetched data of the NUMBER type as the first column of a result set. Because you want to manipulate the NUMBER data without losing precision, cast your result set to OracleResultSet and use getOracleObject to return the NUMBER data in oracle.sql.* format. If you do not cast your result set, then you have to use getObject, which returns your numeric data into a Java Float and loses some of the precision of your SQL data.

The getOracleObject method returns an oracle.sql.NUMBER object into an oracle.sql.Datum return variable unless you cast the output. Cast the getOracleObject output to oracle.sql.NUMBER if you want to use a NUMBER return variable and any of the special functionality of that class.

NUMBER x = (NUMBER)ors.getOracleObject(1);

The setObject and setOracleObject Methods

Just as there is a standard getObject and Oracle-specific getOracleObject in result sets and callable statements, there are also standard setObject and Oracle-specific setOracleObject methods in OraclePreparedStatement and OracleCallableStatement. The setOracleObject methods take oracle.sql.* input parameters.

To bind standard Java types to a prepared statement or callable statement, use the setObject method, which takes a java.lang.Object as input. The setObject method does support a few of the oracle.sql.* types. However, the method has been implemented so that you can enter instances of the oracle.sql.* classes that correspond to the following JDBC standard types: Blob, Clob, Struct, Ref, and Array.

To bind oracle.sql.* types to a prepared statement or callable statement, use the setOracleObject method, which takes a subclass of oracle.sql.Datum as input. To use setOracleObject, you must cast your prepared statement or callable statement to OraclePreparedStatement or OracleCallableStatement.

Example of Using setObject and setOracleObject

For a prepared statement, the setOracleObject method binds the oracle.sql.CHAR data represented by the charVal variable to the prepared statement. To bind the oracle.sql.* data, the prepared statement must be cast to OraclePreparedStatement. Similarly, the setObject method binds the Java String data represented by the variable strVal.

PreparedStatement ps= conn.prepareStatement("text_of_prepared_statement");
((OraclePreparedStatement)ps).setOracleObject(1,charVal);
ps.setObject(2,strVal);

Other setXXX Methods

As with the getXXX methods, there are several specific setXXX methods. Standard setXXX methods are provided for binding standard Java types, and Oracle-specific setXXX methods are provided for binding Oracle-specific types.

Similarly, there are two forms of the setNull method:

  • void setNull(int parameterIndex, int sqlType)

    This is specified in the standard java.sql.PreparedStatement interface. This signature takes a parameter index and a SQL type code defined by the java.sql.Types or oracle.jdbc.OracleTypes class. Use this signature to set an object other than a REF, ARRAY, or STRUCT to NULL.

  • void setNull(int parameterIndex, int sqlType, String sql_type_name)

    With JDBC 2.0, this signature is also specified in the standard java.sql.PreparedStatement interface. This method takes a SQL type name in addition to a parameter index and a SQL type code. Use this method when the SQL type code is java.sql.Types.REF, ARRAY, or STRUCT. If the type code is other than REF, ARRAY, or STRUCT, then the given SQL type name is ignored.

Similarly, the registerOutParameter method has a signature for use with REF, ARRAY, or STRUCT data:

void registerOutParameter
            (int parameterIndex, int sqlType, String sql_type_name)

Binding Oracle-specific types using the appropriate setXXX methods, instead of the methods used for binding standard Java types, may offer some performance advantage.

This section covers the following topics:

Input Data Binding

There are three way to bind data for input:

  • Direct binding where the data itself is placed in a bind buffer

  • Stream binding where the data is streamed

  • LOB binding where a temporary lob is created, the data placed in the LOB using the LOB APIs, and the bytes of the LOB locator are placed in the bind buffer

The three kinds of binding have some differences in performance and have an impact on batching. Direct binding is fast and batching is fine. Stream binding is slower, may require multiple round trips, and turns batching off. LOB binding is very slow and requires many round trips. Batching works, but might be a bad idea. They also have different size limits, depending on the type of the SQL statement.

For SQL parameters, the length of standard parameter types, such as RAW and VARCHAR2, is fixed by the size of the target column. For PL/SQL parameters, the size is limited to a fixed number of bytes, which is 32766.

In Oracle Database 10g release 2 (10.2), certain changes were made to the setString, setCharacterStream, setAsciiStream, setBytes, and setBinaryStream methods of PreparedStatement. The original behavior of these APIs were:

  • setString: Direct bind of characters

  • setCharacterStream: Stream bind of characters

  • setAsciiStream: Stream bind of bytes

  • setBytes: Direct bind of bytes

  • setBinaryStream: Stream bind of bytes

Starting from Oracle Database 10g release 2 (10.2), automatic switching between binding modes, based on the data size and on the type of the SQL statement is provided.

setBytes and setBinaryStream

For SQL, direct bind is used for size up to 2000 and stream bind for larger.

For PL/SQL direct bind is used for size up to 32766 and LOB bind is used for larger.

setString, setCharacterStream, and setAsciiStream

For SQL, direct bind is used up to 32766 Java characters and stream bind is used for larger. This is independent of character set.

For PL/SQL, you must be careful about the byte size of the character data in the database character set or the national character set depending on the setting of the form of use parameter. Direct bind is used for data where the byte length is less than 32766 and LOB bind is used for larger.

For fixed length character sets, multiply the length of the Java character data by the fixed character size in bytes and compare that to the restrictive values. For variable length character sets, there are three cases based on the Java character length, as follows:

  • If character length is less than 32766 divided by the maximum character size, then direct bind is used.

  • If character length is greater than 32766 divided by the minimum character size, then LOB bind is used.

  • If character length is in between and if the actual length of the converted bytes is less than 32766, then direct bind is used, else LOB bind is used.

Note:

When a PL/SQL procedure is embedded in a SQL statement, the binding action is different. Refer to "Data Interface for LOBs" for more information.

The server-side internal driver has the following additional limitations:

  • setString, setCharacterStream, and setASCIIStream APIs are not supported for SQL CLOB columns when the data size in characters is over 4000 bytes

  • setBytes and setBinaryStream APIs are not supported for SQL BLOB columns when the data size is over 2000 bytes

Important:

Do not use these APIs with the server-side internal driver, without careful checking of the data size in client code.

See Also:

JDBC Release Notes for further discussion and possible workarounds

Method setFixedCHAR for Binding CHAR Data into WHERE Clauses

CHAR data in the database is padded to the column width. This leads to a limitation in using the setCHAR method to bind character data into the WHERE clause of a SELECT statement. The character data in the WHERE clause must also be padded to the column width to produce a match in the SELECT statement. This is especially troublesome if you do not know the column width.

To remedy this, Oracle has added the setFixedCHAR method to the OraclePreparedStatement class. This method runs a non-padded comparison.

Note:

  • Remember to cast your prepared statement object to OraclePreparedStatement to use the setFixedCHAR method.

  • There is no need to use setFixedCHAR for an INSERT statement. The database always automatically pads the data to the column width as it inserts it.

Example

The following example demonstrates the difference between the setCHAR and setFixedCHAR methods.

/* Schema is :
 create table my_table (col1 char(10));
 insert into my_table values ('JDBC');
*/
 PreparedStatement pstmt = conn.prepareStatement 
                    ("select count(*) from my_table where col1 = ?");

 pstmt.setString (1, "JDBC");  // Set the Bind Value
 runQuery (pstmt);             // This will print " No of rows are 0"

 CHAR ch = new CHAR("JDBC      ", null);
 ((OraclePreparedStatement)pstmt).setCHAR(1, ch); // Pad it to 10 bytes
 runQuery (pstmt);             // This will print "No of rows are 1"

 ((OraclePreparedStatement)pstmt).setFixedCHAR(1, "JDBC");
  runQuery (pstmt);            // This will print "No of rows are 1"
 
 void runQuery (PreparedStatement ps)
 {    
   // Run the Query
   ResultSet rs = pstmt.executeQuery ();

   while (rs.next())
     System.out.println("No of rows are " + rs.getInt(1));
   
   rs.close();
   rs = null;
 }

Using Result Set Metadata Extensions

The oracle.jdbc.OracleResultSetMetaData interface is JDBC 2.0-compliant but does not implement the getSchemaName and getTableName methods because Oracle Database does not make this feasible.

The following code snippet uses several of the methods in the OracleResultSetMetadata interface to retrieve the number of columns from the EMP table and the numerical type and SQL type name of each column:

DatabaseMetaData dbmd = conn.getMetaData();
ResultSet rset = dbmd.getTables("", "SCOTT", "EMP", null);

 while (rset.next())
 {
   OracleResultSetMetaData orsmd = ((OracleResultSet)rset).getMetaData();
   int numColumns = orsmd.getColumnCount();
   System.out.println("Num of columns = " + numColumns);

   for (int i=0; i<numColumns; i++)
   {
     System.out.print ("Column Name=" + orsmd.getColumnName (i+1));
     System.out.print (" Type=" + orsmd.getColumnType (i + 1) );
     System.out.println (" Type Name=" + orsmd.getColumnTypeName (i + 1));
  }
}

The program returns the following output:

Num of columns = 5
Column Name=TABLE_CAT Type=12 Type Name=VARCHAR2
Column Name=TABLE_SCHEM Type=12 Type Name=VARCHAR2
Column Name=TABLE_NAME Type=12 Type Name=VARCHAR2
Column Name=TABLE_TYPE Type=12 Type Name=VARCHAR2
Column Name=TABLE_REMARKS Type=12 Type Name=VARCHAR2

Using SQL CALL and CALL INTO Statements

You can use the CALL statement to execute a routine from within SQL.

Note:

A routine is a procedure or a function that is standalone or is defined within a type or package. You must have EXECUTE privilege on the standalone routine or on the type or package in which the routine is defined. Refer to the "Oracle Database SQL Language Reference" for more information about using the CALL statement.

You can execute a routine in two ways:

You can specify one or more arguments to the routine, if the routine takes arguments. You can use positional, named, or mixed notation for argument.

CALL INTO Statement

The INTO clause applies only to calls to functions. You can use the following types of variables with this clause:

PL/SQL Blocks

The basic unit in PL/SQL is a block. All PL/SQL programs are made up of blocks, which can be nested within each other. A PL/SQL block has three parts: a declarative part, an executable part, and an exception-handling part. You get the following advantages by using PL/SQL blocks in your application: