Home/ Questions/Q 934353
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-15T20:59:09+00:00

I’m trying to create a trigger that will do the following. After insert on

  • 0

I’m trying to create a trigger that will do the following.

After insert on Table A, query Table B based on an id (TableA.id=TableB.id) and insert corresponding info into TableA

I have a feeling I’m way off so far so any help would be appreciated

CREATE OR REPLACE TRIGGER myTrig
AFTER INSERT
ON TABLEA
BEGIN
  INSERT INTO TABLEA
  SELECT TABLEB.FIRST_NAME, TABLEB.LAST_NAME, SYSDATE
  FROM TABLEA JOIN TABLEB ON 
  TABLEA.STUDENT_ID=TABLEB.STUDENT_ID
  insert into TABLEA values (....);
END;
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    This will not work. Just think about what you are asking. You want a trigger that fires when a row is inserted into tableA to insert a row into tableA. When would the trigger stop firing?

    Oracle is smart enough to step in and prevent the trigger spiralling into infinity:

    SQL> create or replace trigger t69_after_ins
  2      after insert on t69
  3  begin
  4      insert into t69 values ('blah', 'blah', 99);
  5  end;
  6  /

Trigger created.

SQL>

    Here’s what happens:

    SQL> insert into t69 values ('this', 'that', 1)      
   2  /

insert into t69 values ('this', 'that', 1)
            *
ERROR at line 1:
ORA-00036: maximum number of recursive SQL levels (50) exceeded
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_INS'
ORA-06512: at "APC.T69_AFTER_INS", line 2
ORA-04088: error during execution of trigger 'APC.T69_AFTER_I


SQL>

    “Is there any way that I can update
    TableA based on info from TableB given
    an id that is in both tables? “

    If by “update” you actually do mean UPDATE, and – crucially – depending on the precise logic you wish to implement then perhaps yes:

    SQL> create or replace trigger t69_after_ins
  2      after insert on t69
  3  begin
  4      update t69
  5          set name = ( select name from t23
  6                       where t23.id = t69.id )
  7          where name is null;
  8  end;
  9  /

Trigger created.

SQL> insert into t69 (id, name) values (122, null)
  2  /

1 row created.

SQL> select name from t69
  2  where id = 122
  3  /

NAME
----------
MAISIE

SQL>

    However this remains a bad idea. Triggers are hard to understand and can have a deleterious nimpact on the performance of our SQL. So I suggest you try to figure out a way of building your logic into the main body of your application, rather than trying to use a trigger.

    • 0