The DBMS_LOB.APPEND procedure in Oracle Database is part of the DBMS_LOB package, which provides a collection of procedures and functions for managing Large Objects (LOBs). LOBs in Oracle are used to store large amounts of data, such as text, images, videos, and documents, that are too large to be efficiently stored in standard data types. The DBMS_LOB.APPEND procedure specifically is used to append the content of one LOB (source LOB) to another LOB (destination LOB).
Here is an overview of the DBMS_LOB.APPEND procedure:
DBMS_LOB.APPEND ( dest_lob IN OUT NOCOPY BLOB | CLOB | NCLOB, src_lob IN BLOB | CLOB | NCLOB );
dest_lob: The LOB (either BLOB, CLOB, or NCLOB) to which the contents will be appended. This parameter is both an input and output parameter, meaning the procedure modifies this LOB directly.
src_lob: The LOB whose contents are to be appended to dest_lob. This parameter is an input-only parameter.
Data Type Support: It supports Binary Large Objects (BLOBs), Character Large Objects (CLOBs), and National Character Large Objects (NCLOBs).
In-Place Modification: The append operation modifies the destination LOB in place. This means that after the operation, the dest_lob will contain its original data followed by the data from src_lob.
Efficiency: This procedure is optimized for handling large volumes of data efficiently, without the need for intermediate storage or excessive memory usage.
Consider you have two CLOBs, clob1 and clob2, and you want to append the content of clob2 to clob1. The following PL/SQL block demonstrates how to use DBMS_LOB.APPEND:
BEGIN -- Assuming clob1 and clob2 are already initialized and populated DBMS_LOB.APPEND(clob1, clob2); -- At this point, clob1 contains its original data followed by the data from clob2 END;
Transaction Management: The append operation is part of the transaction that encloses the DBMS_LOB.APPEND call. If the transaction is rolled back, the append operation is also undone.
Permissions: The user executing the DBMS_LOB.APPEND procedure must have the necessary permissions to access and modify the LOBs involved.
Temporary LOBs: The procedure can also work with temporary LOBs, which are useful for short-lived, large-volume data processing.
In summary, DBMS_LOB.APPEND is a powerful tool in Oracle for efficiently managing large data concatenations directly within the database, enabling seamless and efficient manipulation of large object data types.