JDBC Type 4 Driver Programmer's Reference for SQL/MX Release 3.1 (H06.23+, J06.12+)

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Reading Unicode data from a CLOB Column

To read Unicode or MBCS data from a CLOB column, use the CLOB interface or Reader.

Using the

CLOB interface:

// Obtain the Clob from ResultSet

Clob myClob = rs.getClob("myClobColumn");

// Obtain the input stream to read Clob data

Reader cs = myClob.getCharacterStream();

// read Clob data using Reader

char[] myClobData;

myClobData = new char[length];

cs.read(myClobData, offset, length);

To read Unicode data from a CLOB column by using a Reader:

// obtain the Reader from ResultSet

Reader cs = rs.getCharacterStream("myClobColumn");

// read Clob data using the InputStream

char[] myClobData;

myClobData = new char[length];

css.read(myClobData, offset, length);

Updating CLOB Data

Updating Clob Objects with the updateClob Method

Replacing Clob Objects

To update CLOB data, use the methods in the Clob interface or use the updateClob method of the ResultSet interface. The Type 4 driver makes

changes directly to the

CLOB data. Therefore, the Type 4 driver returns false to the locatorsUpdateCopy method of the DatabaseMetaData

interface. Applications do not need to issue a separate update statement to update the CLOB data.

Make updates to

CLOB data in the following ways:

Updating Clob Objects with the updateClob Method

Replacing Clob Objects

Updating Clob Objects with the updateClob Method

Unlike some LOB support implementations, the Type 4 driver updates the CLOB data directly in the database. So, when the Clob object is same

in the

updateClob method as the Clob object obtained using getClob, the updateRow method of the ResultSet interface does nothing with the

Clob object.

When the

Clob objects differ, the Clob object in the updateClob method behaves as if the setClob method was issued. See Inserting a Clob

Object with the setClob Method.

Replacing Clob Objects

You can replace Clob objects in the following ways:

Use the EMPTY_CLOB() function to replace the Clob object with the empty Clob object, then insert new data as described under Inserting

CLOB Columns by Using the Clob Interface.

Use the PreparedStatement.setAsciiStream() or setCharacterStream() method to replace the existing Clob object with new CLOB data.

Use the setClob or updateClob method to replace the existing CLOB objects as explained under Inserting a Clob Object with the setClob

Method and Updating Clob Objects with the updateClob Method.

Deleting CLOB Data

To delete CLOB data, the JDBC application uses the SQL DELETE statement to delete the row in the base table.

When the row containing the

CLOB column is deleted by the JDBC application, the corresponding CLOB data is automatically deleted by the delete

trigger associated with the base table. For information about triggers, see

Using SQL/MX Triggers to Delete LOB Data.