ora-04091 table is Mutating-

Question

I\'m using a function which compares all the columns in Table 1 and Table 2 and returns \'Y\' or \'N\'. Based on that, I will update my Table 1.

But when I run the merge

Answer 1

Chade i tried this Option it didnt throw me any error.

CREATE OR REPLACE PROCEDURE updatetabble1 AS
    BEGIN
        MERGE
        INTO Table1 DBC
        USING  (            Select ename from
            (
            Select ename
            from
                (
                Select ename, column1||Column2||Column3 from table1
                union
                Select ename, column1||Column2||Column3 from table2 
                ) 
            ) 
        GROUP BY ename HAVING count(*) > 1
        ) TBL_MAIN
                 ON ( DBC.empname = TBL_MAIN.empname)
                WHEN MATCHED THEN
 UPDATE SET DBC.DATA_CHANGED = 'Y';
COMMIT;     
END updatetabble1;

Answer 2

You might consider using a temporary table, I.E.:

create global temporary table table12_gt(empname varchar2(30), is_changed char(1));

CREATE OR REPLACE PROCEDURE updatetabble1_2 AS
  BEGIN
   insert into table12_gt
    select empname,
           CASE
             WHEN count(v) > 1 THEN
              'Y'
             ELSE
              'N'
           END is_changed
      from (SELECT empname, trim(column1 || column2 || column3) v
              FROM table1
            UNION
            SELECT empname, trim(column1 || column2 || column3) v FROM table2)
     GROUP BY empname;

  MERGE INTO Table1 DBC
  USING (SELECT empname, is_changed as DATA_CHANGED FROM table12_gt) TBL_MAIN
  ON (DBC.empname = TBL_MAIN.empname)
  WHEN MATCHED THEN
    UPDATE SET DBC.DATA_CHANGED = TBL_MAIN.DATA_CHANGED;

  COMMIT;
END updatetabble1_2;

This quite "quick and dirty" but can be a start