Get Generated Keys From Preparedstatement

Oracle Java Database Connectivity (JDBC) supports several different versions of JDBC, including JDBC 2.0 and 3.0. This chapter provides an overview of JDBC 2.0 and JDBC 3.0 support in the Oracle JDBC drivers. The chapter contains the following sections:

• Get Generated Keys From Preparedstatement Iphone
• Get Generated Keys From Preparedstatement 2017
• Get Generated Keys From Preparedstatement Excel
• Java Prepared Statement Get Generated Keys

Feb 04, 2017  connection = dataSource.getConnection; statement = connection.prepareStatement(sql, Statement.RETURNGENERATEDKEYS); result = statement.executeUpdate. How to get primary key value (auto-generated keys) from inserted queries using JDBC? JDBC Object Oriented Programming Programming If you insert records into a table which contains auto-incremented column, using a Statement or, PreparedStatement objects.

Introduction

The Oracle JDBC drivers support all JDBC 3.0 features. These features are provided through the oracle.jdbc and oracle.sql packages. These packages support all Java Development Kit (JDK) releases from 1.2 through 1.4. JDBC 3.0 features that depend on JDK1.4 are made available to earlier JDK versions through Oracle extensions.

Get Generated Keys From Preparedstatement Iphone

JDBC 2.0 Support: JDK 1.2.x and Later Versions

Standard JDBC 2.0 features are supported by JDK 1.2 and later versions. There are three areas to consider:

• Support for data types, such as objects, arrays, and large objects (LOBs). This is handled through the standard java.sql package.

• Support for standard features, such as result set enhancements and update batching. This is handled through standard objects, such as Connection, ResultSet, and PreparedStatement, under JDK 1.2.x and later.

• Support for extended features, such as features of the JDBC 2.0 optional package, also known as the standard extension application programming interface (API), including data sources, connection pooling, and distributed transactions.

This section covers the following topics:

Note:

JDK1.1.x is no longer supported. The package oracle.jdbc2 has been removed.

Data Type Support

Oracle JDBC fully supports JDK 1.2.x, which includes standard JDBC 2.0 functionality through implementation of interfaces in the standard java.sql package. These interfaces are implemented as appropriate by classes in the oracle.sql and oracle.jdbc packages.

Standard Feature Support

In a JDK 1.2.x environment, using the JDBC classes in classes12.jar, JDBC 2.0 features, such as scrollable result sets, updatable result sets, and update batching, are supported through methods specified by standard JDBC 2.0 interfaces.

Extended Feature Support

Features of the JDBC 2.0 optional package, including data sources, connection pooling, and distributed transactions, are supported in a JDK 1.2.x or later environment.

The standard javax.sql package and classes that implement its interfaces are included in the Java Archive (JAR) files packaged with the Oracle Database.

Standard versus Oracle Performance Enhancement APIs

The following performance enhancements are available under JDBC 2.0, which had previously been available as Oracle extensions:

• Update batching

• Fetch size or row prefetching

In each case, you have the option of using the standard model or the Oracle model. Do not, however, try to mix usage of the standard model and Oracle model within a single application for either of these features.

See Also:

JDBC 3.0 Support: JDK 1.4 and Previous Releases

Table 4-1 lists the interfaces and classes added or extended to support specific JDBC features.

Table 4-1 JDBC 3.0 Feature Support

New feature	JDK1.4 implementation	Pre-JDK1.4 implementation
Savepoints (new class)	java.sql.Savepoint	oracle.jdbc.OracleSavepoint
Savepoints (connection extensions)	java.sql.connection	oracle.jdbc.OracleConnection
Querying parameter capacities (new class)	java.sql.ParameterMetaData	oracle.jdbc.OracleParameterMetaData
Querying parameter capacities (interface change)	Not applicable	oracle.jdbc.OraclePreparedStatement
Resource adapters	oracle.jdbc.connector	oracle.jdbc.connector
RowSets	oracle.jdbc.rowset	oracle.jdbc.rowset
LOB modification	Not applicable	oracle.sql.BLOBoracle.sql.CLOB
Retrieving auto-generated keys	oracle.sql.Statement	oracle.jdbc.OracleStatement oracle.jdbc.OracleConnection
Result set holdability	java.sql.Connection java.sql.DatabaseMetaData java.sql.Statement	oracle.jdbc.OracleConnection oracle.jdbc.OracleDatabaseMetadata oracle.jdbc.OracleStatement

Overview of Supported JDBC 3.0 Features

Table 4-2 lists the JDBC 3.0 features supported at this release and gives references to a detailed discussion of each feature.

Table 4-2 Key Areas of JDBC 3.0 Functionality

Feature	Comments and References
Transaction savepoints	See 'Transaction Savepoints' for information.
Statement caching	Reuse of prepared statements by connection pools. See Chapter 22, 'Statement Caching'.
Switching between local and global transactions	See 'Switching Between Global and Local Transactions'.
LOB modification	See 'JDBC 3.0 LOB Interface Methods' .
Named SQL parameters	See 'Interface oracle.jdbc.OracleCallableStatement' and 'Interface oracle.jdbc.OraclePreparedStatement' .
RowSets	See Chapter 20, 'JDBC RowSets'
Retrieving auto-generated keys	See 'Retrieval of Auto-Generated Keys'
Result set holdability	See 'Result Set Holdability'

Transaction Savepoints

The JDBC 3.0 specification supports savepoints, which offer finer demarcation within transactions. Applications can set a savepoint within a transaction and then roll back all work done after the savepoint. Savepoints relax the atomicity property of transactions. A transaction with a savepoint is atomic in the sense that it appears to be a single unit outside the context of the transaction, but code operating within the transaction can preserve partial states.

Note:

Savepoints are supported for local transactions only. Specifying a savepoint within a global transaction causes SQLException to be thrown.

JDK1.4 specifies a standard savepoint API. Oracle JDBC provides the following different savepoint interfaces:

• java.sql.Savepoint

  Works with JDK1.4

• oracle.jdbc.OracleSavepoint

  Works across all supported JDK versions.

JDK1.4 adds savepoint-related APIs to java.sql.Connection. The Oracle JDK version-independent interface, oracle.jdbc.OracleConnection, provides equivalent functionality.

Creating a Savepoint

You create a savepoint using either Connection.setSavepoint, which returns a java.sql.Savepoint instance, or OracleConnection.oracleSetSavepoint, which returns an oracle.jdbc.OracleSavepoint instance.

A savepoint is either named or unnamed. You specify the name of a savepoint by supplying a string to the setSavepoint method. If you do not specify a name, then the savepoint is assigned an integer ID. You retrieve a name using getSavepointName(). You retrieve an ID using getSavepointId().

Note:

Attempting to retrieve a name from an unnamed savepoint or attempting to retrieve an ID from a named savepoint throws an SQLException.

Rolling back to a Savepoint

You roll back to a savepoint using Connection.rollback(Savepoint svpt) or OracleConnection.oracleRollback(OracleSavepoint svpt). If you try to roll back to a savepoint that has been released, then SQLException is thrown.

Releasing a Savepoint

You remove a savepoint using one of the following methods:

• Connection.releaseSavepoint(Savepoint svpt)

• OracleConnection.oracleReleaseSavepoint(OracleSavepoint svpt)

Note:

As of Oracle Database 10g, releaseSavepoint and oracleReleaseSavepoint are not supported. If you call either of the methods, then SQLException is thrown with the message 'Unsupported feature'.

Checking Savepoint Support

You query whether savepoints are supported by your database by calling oracle.jdbc.OracleDatabaseMetaData.supportsSavepoints(), which returns true if savepoints are available, false otherwise.

Savepoint Notes

When using savepoints, you must consider the following:

• After a savepoint has been released, attempting to reference it in a rollback operation will cause an SQLException to be thrown.

• When a transaction is committed or rolled back, all savepoints created in that transaction are automatically released and become invalid.

• Rolling a transaction back to a savepoint automatically releases and makes invalid any savepoints created after the savepoint in question.

Savepoint Interfaces

The following methods are used to get information from savepoints. These methods are defined within both the java.sql.Connection and oracle.jdbc.OracleSavepoint interfaces:

• public int getSavepointId() throws SQLException;

  Returns the savepoint ID for an unnamed savepoint. Throws SQLException if self is a named savepoint.

• public String getSavepointName() throws SQLException;

  Returns the name of a named savepoint. Throws SQLException if self is an unnamed savepoint.

The following methods are defined within the java.sql.Connection interface:

• public Savepoint setSavepoint() throws SQLException;

  Creates an unnamed savepoint. Throws SQLException on database error or if connection is in the auto-commit mode or participating in a global transaction.

• public Savepoint setSavepoint(String name) throws SQLException;

  Creates a named savepoint. If a savepoint by this name already exists, then this instance replaces it. Throws SQLException on database error or if connection is in the auto-commit mode or participating in a global transaction.

• public void rollback(Savepoint savepoint) throws SQLException;

  Removes specified savepoint from current transaction. Any references to the savepoint after it is removed cause an SQLException to be thrown. Throws SQLException on database error or if connection is in the auto-commit mode or participating in a global transaction.

• public void releaseSavepoint(Savepoint savepoint) throws SQLException;

  Not supported at this release. Always throws SQLException.

Pre-JDK1.4 Savepoint Support

The following methods are defined within the oracle.jdbc.OracleConnection interface. Except for using OracleSavepoint in the signatures, they are identical to the methods declared in the preceding section.

Retrieval of Auto-Generated Keys

Many database systems automatically generate a unique key field when a row is inserted. Oracle Database provides the same functionality with the help of sequences and triggers. JDBC 3.0 introduces the retrieval of auto-generated keys feature that enables you to retrieve such generated values. In JDBC 3.0, the following interfaces are enhanced to support the retrieval of auto-generated keys feature:

These interfaces provide methods that support retrieval of auto-generated keys. However, this feature is supported only when INSERT statements are processed. Other data manipulation language (DML) statements are processed, but without retrieving auto-generated keys.

Note:

The Oracle server-side internal driver does not support the retrieval of auto-generated keys feature.

java.sql.DatabaseMetaData

In JDBC 3.0, the java.sql.DatabaseMetaData interface provides the following method:

The method indicates whether retrieval of auto-generated keys is supported or not by the JDBC driver and the underlying data source.

Get Generated Keys From Preparedstatement 2017

java.sql.Statement

The java.sql.Statement interface is enhanced with the following methods:

This interface provides new methods for processing SQL statements and retrieving auto-generated keys. These methods take a String object that contains a SQL statement. They also take either the flag, Statement.RETURN_GENERATED_KEYS, indicating whether any generated columns are to be returned, or an array of column names or indexes specifying the columns that should be returned. The flag and the array values are considered only when an INSERT statement is processed. If an UPDATE or DELETE statement is processed, these values are ignored.

The getGeneratedKeys() method enables you to retrieve the auto-generated key fields. The auto-generated keys are returned as a ResultSet object.

If key columns are not explicitly indicated, then Oracle JDBC drivers cannot identify which columns need to be retrieved. When a column name or column index array is used, Oracle JDBC drivers can identify which columns contain auto-generated keys that you want to retrieve. However, when the Statement.RETURN_GENERATED_KEYS integer flag is used, Oracle JDBC drivers cannot identify these columns. When the integer flag is used to indicate that auto-generated keys are to be returned, the ROWID pseudo column is returned as key. The ROWID can be then fetched from the ResultSet object and can be used to retrieved other columns.

java.sql.Connection

The java.sql.Connection interface is enhanced with the following methods:

These methods enable you to create a PreparedStatement object that is capable of returning auto-generated keys.

Sample Code

The following code illustrates retrieval of auto-generated keys:

In the preceding example, a sequence, SEQ01, is created to generate values for the ORDER_ID column starting from 1000 and incrementing by 1 each time the sequence is processed to generated the next value. An OraclePreparedStatement object is created to insert a row in to the ORDERS table.

JDBC 3.0 LOB Interface Methods

Before Oracle Database 10g release 2 (10.2), Oracle provided proprietary interfaces for modification of LOB data. JDBC 3.0 adds methods for these operations. In Oracle9i Database release 2, the JDBC 3.0 methods were present in ojdbc14.jar, but were not functional. The JDBC 3.0 standard LOB methods differ slightly in name and function from the Oracle proprietary ones. In Oracle Database 10g release 2 (10.2), the JDBC 3.0 standard methods are implemented in both ojdbc14.jar and classes12.jar. In order to use these methods with JDK1.2 or 1.3, LOB variables must be typed as, or cast to, oracle.sql.BLOB or oracle.sql.CLOB as appropriate. With JDK1.4, LOB variables may be typed as java.sql.Blob or java.sql.Clob.

Table 4-3 and Table 4-4 show the conversions between Oracle proprietary methods and JDBC 3.0 standard methods.

Table 4-3 BLOB Method Equivalents

Oracle Proprietary Method	JDBC 3.0 Standard Method
putBytes(long pos, byte [] bytes)	setBytes(long pos, byte[] bytes)
putBytes(long pos, byte [] bytes, int length)	setBytes(long pos, byte[] bytes, int offset, int len)
getBinaryOutputStream(long pos)	setBinaryStream(long pos)
trim (long len)	truncate(long len)

Table 4-4 CLOB Method Equivalents

Oracle Proprietary Method	JDBC 3.0 Standard Method
putString(long pos, String str)	setString(long pos, String str)
not applicable	setString(long pos, String str, int offset, int len)
getAsciiOutputStream(long pos)	setAsciiStream(long pos)
getCharacterOutputStream(long pos)	setCharacterStream(long pos)
trim (long len)	truncate(long len)

Result Set Holdability

Result set holdability is a new feature introduced in JDBC 3.0. This feature enables applications to decide whether the ResultSet objects should be open or closed, when a commit operation is performed. The commit operation could be either implicit or explicit.

The default holdability property of a ResultSet object is implementation defined. The default holdability of ResultSet objects returned by the underlying data source can be determined using the APIs provided by JDBC 3.0.

In JDBC 3.0, the following APIs have been modified to support this feature:

• java.sql.Connection

• java.sql.DatabaseMetaData

• java.sql.Statement

JDBC 3.0 also provides two new ResultSet constants:

• ResultSet.HOLD_CURSORS_OVER_COMMIT

• ResultSet.CLOSE_CURSORS_AT_COMMIT

Oracle Database only supports HOLD_CURSORS_OVER_COMMIT. Therefore, it is the default value for the Oracle JDBC drivers. Any attempt to change holdability will throw SQLException.

• Related Questions & Answers

• Selected Reading

While creating a table, in certain scenarios, we need values to column such as ID, to be generated/incremented automatically. Various databases support this feature in different ways.

In MySQL database you can declare a column auto increment using the following syntax.

Get Generated Keys From Preparedstatement Excel

While inserting records in a table there is no need to insert value under the auto-incremented column. These will be generated automatically.

For example, in a table if we have a column with name ID and data type INT, which is auto-incremented and, if we already have 6 records in that table. When you insert the next record using the INSERT statement the ID value of the new record will be 7 and the ID value of its next record will be 8.

(You can specify the initial value and interval for these auto-incremented columns).

Retrieving the auto-incremented values

If you insert records into a table which contains auto-incremented column, using a PreparedStatement object.

You can retrieve the values of that particular column, generated by the current PreparedStatement object using the getGeneratedKeys() method.

Example

Let us create a table with name sales in MySQL database, with one of the columns as auto-incremented, using CREATE statement as shown below −

Now, to insert records into this table using PreparedStatement object and, to retrieve the auto-incremented values generated by it −

• Register the Driver class of the desired database using the registerDriver() method of the DriverManager class or, the forName() method of the class named Class.

• Create a Connection object by passing the URL of the database, user-name and password of a user in the database (in string format) as parameters to the getConnection() method of the DriverManager class.

• Create a PreparedStatement object using the prepareStatement() method of the connection interface.

To this method pass the INSERT statement with bind variables in string format as one parameter and, Statement.RETURN_GENERATED_KEYS as other parameter as −

• Set values of each record to the bind variables using the setXXX() methods and, add it to batch.

After adding values of all the records to the batch, execute the batch using the executeBatch() method.

• Finally, get the auto-incremented keys generated by this PreparedStatement object using the getGeneratedKeys() method.

Following JDBC program inserts 5 records into the Sales table (created above) using PreparedStatement, retrieves and displays the auto-incremented values generated by it.

Example

Java Prepared Statement Get Generated Keys

Output