To delete child records manually without using oracle's delete cascade

Question

Hi all
I have to write a procedure that accepts schema name, table name and column value as parameters....I knew that i need to use metadata to do that deleting manually....I am a beginner...can somebody help me with the procedure?

Answer 1

Hi Guru,
They told me to use this procedure...but this procedure isn't working...can you help me to understand this procedure?
CREATEOR REPLACE PROCEDURE delete_cascade(
    table_owner          VARCHAR2,
    parent_table         VARCHAR2,
    where_clause         VARCHAR2
)IS
    /*   Example call:  execute delete_cascade('MY_SCHEMA', 'MY_MASTER', 'where ID=1'); */
    child_cons     VARCHAR2(30);
    parent_cons    VARCHAR2(30);
    child_table    VARCHAR2(30);
    child_cols     VARCHAR(500);
    parent_cols    VARCHAR(500);
    delete_command VARCHAR(10000);
    new_where_clause VARCHAR2(10000);
    /* gets the foreign key constraints on other tables which depend on columns in parent_table */
    CURSOR cons_cursor IS
        SELECT owner, constraint_name, r_constraint_name, table_name, delete_rule
          FROM all_constraints
         WHERE constraint_type ='R'
           AND delete_rule ='NO ACTION'
           AND r_constraint_name IN(SELECT constraint_name
                                       FROM all_constraints
                                      WHERE constraint_type IN('P','U')
                                        AND table_name = parent_table
                                        AND owner = table_owner)
           ANDNOT table_name = parent_table;-- ignore self-referencing constraints
    /* for the current constraint, gets the child columns and corresponding parent columns */
    CURSOR columns_cursor IS
        SELECT cc1.column_name AS child_col, cc2.column_name AS parent_col
          FROM all_cons_columns cc1, all_cons_columns cc2
         WHERE cc1.constraint_name = child_cons
           AND cc1.table_name = child_table
           AND cc2.constraint_name = parent_cons
           AND cc1.position = cc2.position
        ORDERBY cc1.position;
BEGIN
    /* loops through all the constraints which refer back to parent_table */
    FOR cons IN cons_cursor LOOP
        child_cons   := cons.constraint_name;
        parent_cons  := cons.r_constraint_name;
        child_table  := cons.table_name;
        child_cols   :='';
        parent_cols  :='';
        /* loops through the child/parent column pairs, building the column lists of the DELETE statement */
        FOR cols IN columns_cursor LOOP
            IF child_cols ISNULLTHEN
                child_cols  := cols.child_col;
            ELSE
                child_cols  := child_cols ||', '|| cols.child_col;
            ENDIF;
            IF parent_cols ISNULLTHEN
                parent_cols  := cols.parent_col;
            ELSE
                parent_cols  := parent_cols ||', '|| cols.parent_col;
            ENDIF;
        END LOOP;
        /* construct the WHERE clause of the delete statement, including a subquery to get the related parent rows */
        new_where_clause  :=
            'where ('|| child_cols ||') in (select '|| parent_cols ||' from '|| table_owner ||'.'|| parent_table ||
            ' '|| where_clause ||')';
        delete_cascade(cons.owner, child_table, new_where_clause);
    END LOOP;
    /* construct the delete statement for the current table */
    delete_command  :='delete from '|| table_owner ||'.'|| parent_table ||' '|| where_clause;
    -- this just prints the delete command
    DBMS_OUTPUT.put_line(delete_command ||';');
        EXECUTE IMMEDIATE delete_command;
    -- remember to issue a COMMIT (not included here, for safety)
END;Edited by: BluShadow on 09-Oct-2012 16:05
added {noformat}{noformat} tags for readability.  Please read: {message:id=9360002} and learn to do this yourself in future.