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

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To read binary data from the BLOB column, use the Blob interface or InputStream.

Using the

Blob interface:

// Obtain the Blob from ResultSet

Blob myBlob = rs.getBlob("myBlobColumn");

// Obtain the input stream to read Blob data

InputStream is = myBlob.getBinaryStream();

// read Blob data using the InputStream

byte[] myBlobData;

myBlobData = new byte[length];

is.read(myBlobData, offset, length);

Using InputStream:

// obtain the InputStream from ResultSet

InputStream is = rs.getBinaryStream("myBlobColumn");

// read Blob data using the InputStream

byte[] myBlobData;

myBlobData = new byte[length];

is.read(myBlobData, offset, length);

Updating BLOB Data

Updating Blob Objects by Using the updateBlob Method

Replacing Blob Objects

To update BLOB data, use the methods in the Blob interface or use the updateBlob method of the ResultSet interface. The Type 4 driver makes

changes to the

BLOB data directly. 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 BLOB data.

Update BLOB data in the following ways.

Updating Blob Objects by using the updateBlob Method

Replacing Blob Objects

Updating Blob Objects by Using the updateBlob Method

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

in the

updateBlob method as the object obtained using getBlob, the updateRow method of the ResultSet interface does nothing with the Blob

object.

When the Blob objects differ, the Blob object in the updateBlob method behaves as if the setBlob method was issued. See Inserting a Blob

Object with the setBlob Method.

Replacing Blob Objects

You can replace Blob objects in the following ways:

Use the EMPTY_BLOB() function to replace the Blob object with the empty Blob object.

Replace an existing Blob object in a row by inserting the Blob with new data as described under Inserting a BLOB Column Using the Blob

Interface.

Use the setBinaryStream() method to of the PreparedStatement interface to replace the existing Blob object with new BLOB data.

Use the setBlob or updateBlob methods to replace the existing BLOB objects as explained under Inserting a Blob Object with the setBlob

Method and Updating Blob Objects with the UpdateBlob Method.

Deleting BLOB Data

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

When the row containing the

BLOB column is deleted by the application, the corresponding BLOB 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.