After insert or update calculate column

Question

question about a table.
I have a table called table1
AFTER data is inserted or updated into the table1
I want to run an update on the same table (table1) with a case statement
update table1
set column2 = case
WHEN column1 = 'abc' THEN 'testl'
WHEN column1 = 'def' THEN 'test2'
ELSE 'test3'
END;
commit;
END;
i cant use a trigger because i get error since the insert would be on same table.
What else can i use for this update ? I cant use a stored procedure that runs daily or something like that because the column2 in the table needs to be populated immediately after an insert or update
thanks for any ideas

Answer 1

SQL>  CREATE TABLE TABLE1
  2  (
  3    COLUMN1 VARCHAR2(10),
  4    COLUMN2 VARCHAR2(10)
  5  );
Table created.
SQL> CREATE OR REPLACE TRIGGER TRG_TABLE1
  2  BEFORE INSERT OR UPDATE OF COLUMN1 ON TABLE1
  3  FOR EACH ROW
  4  BEGIN
  5
  6  IF :NEW.COLUMN1 = 'abc' THEN
  7     :NEW.COLUMN2 := 'test1';
  8  ELSIF :NEW.COLUMN1 = 'def' THEN
  9     :NEW.COLUMN2 := 'test2';
10  ELSE
11     :NEW.COLUMN2 := 'test3';
12  END IF;
13
14  END;
15  /
Trigger created.
SQL> INSERT INTO TABLE1(COLUMN1) VALUES('abc');
1 row created.
SQL> SELECT * FROM TABLE1;
COLUMN1    COLUMN2
abc        test1
SQL> UPDATE TABLE1 SET COLUMN1 = 'def';
1 row updated.
SQL> SELECT * FROM TABLE1;
COLUMN1    COLUMN2
def        test2
SQL>
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