Merge row count

A simple utility PL/SQL Package to allow counting of rows inserted/updated/deleted by merge operation in Oracle.

The need for package

Oracle does not provide functionality for obtaining number of rows that were

• inserted
• updated
• deleted

when using a MERGE operation to do it all.

This simple utility is to fill the gap in the functionality.

Be aware that using the utility to count the data processed will have slight, but negative impact on the performance of Merge operation. This is due to the fact of overhead of SQL - PL/SQL context switching.

Usage samples

Sample setup

CREATE TABLE emp(id INTEGER PRIMARY KEY, first_name VARCHAR2(50));

INSERT INTO emp
SELECT rownum AS id, 'emp '||rownum AS first_name
  FROM DUAL
 CONNECT BY LEVEL <= 50;

 COMMIT;

You need to call the counter functions on MERGE block, to count the rows processed.

BEGIN
  MERGE INTO emp dst
    USING (SELECT rownum AS id, 'emp '||rownum AS first_name
             FROM DUAL
            CONNECT BY LEVEL <= 100
          ) src
       ON (src.id = dst.id)
    WHEN MATCHED THEN
      UPDATE
         SET dst.first_name = src.first_name
       WHERE merge_row_count.upd() > 0
      DELETE
       WHERE src.id <= 10
         AND merge_row_count.del() > 0
    WHEN NOT MATCHED THEN
      INSERT (dst.id, dst.first_name)
      VALUES (src.id, src.first_name)
       WHERE merge_row_count.ins() > 0;
  DBMS_OUTPUT.PUT_LINE( SQL%ROWCOUNT );
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_inserted()  || ' rows inserted.');
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_updated()   || ' rows updated.' );
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_deleted()   || ' rows deleted.' );
  ROLLBACK;
END;
/

In the above example the package function is called from within the MERGE statement one call for each UPDATE, DELETE and INSERT operation is done

For performance reasons it's better to have your merge statements make as little PLSQL context switching as possible. You may call the merge operation wit a counter used only on the part that is likely to process less rows. If your code is suppose to mainly update existing rows and sometimes insert new rows it might be better to use calls only to merge_row_count.ins()

BEGIN
  MERGE INTO emp dst
    USING (SELECT rownum AS id, 'emp '||rownum AS first_name
             FROM DUAL
            CONNECT BY LEVEL <= 100
          ) src
       ON (src.id = dst.id)
    WHEN MATCHED THEN
      UPDATE
         SET dst.first_name = src.first_name
    WHEN NOT MATCHED THEN
      INSERT (id, first_name)
      VALUES (src.id, src.first_name)
       WHERE merge_row_count.ins() > 0;
  DBMS_OUTPUT.PUT_LINE( SQL%ROWCOUNT );
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_inserted()  || ' rows inserted.');
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_updated()   || ' rows updated.' );
  ROLLBACK;
END;
/

If your code is suppose to mainly insert new rows and sometimes update existing rows it might be better to use calls only to merge_row_count.upd()

BEGIN
  MERGE INTO emp dst
    USING (SELECT rownum AS id, 'emp '||rownum AS first_name
             FROM DUAL
            CONNECT BY LEVEL <= 100
          ) src
       ON (src.id = dst.id)
    WHEN MATCHED THEN
      UPDATE
         SET dst.first_name = src.first_name
       WHERE merge_row_count.upd() > 0
    WHEN NOT MATCHED THEN
      INSERT (id, first_name)
      VALUES (src.id, src.first_name);
  DBMS_OUTPUT.PUT_LINE( SQL%ROWCOUNT );
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_inserted()  || ' rows inserted.');
  DBMS_OUTPUT.PUT_LINE( merge_row_count.get_updated()   || ' rows updated.' );
  ROLLBACK;
END;
/