Really Simple Date conversion function... but doesn't work

Question

For my application I need a function that converts a date to a date that is a monday.
I wrote this simple function, and I've been trying for many many times... but it just doesn't work. It returns a null value. The problem lies with the IF-statement.
I'm using iSQL 9
CREATE OR REPLACE FUNCTION to_monday ( datum IN DATE )
  RETURN DATE
  AS
BEGIN
  FOR n IN 0..6 LOOP
    IF ( TO_CHAR(datum + n, 'day') = 'friday' ) THEN
      RETURN (datum + n - 4);
    END IF;
  END LOOP;
END;
SELECT to_monday(CURRENT_DATE) FROM dual;Edited by: popovitsj on 11-mrt-2012 5:07
Edited by: popovitsj on 11-mrt-2012 5:09
Edited by: popovitsj on 11-mrt-2012 5:09
Edited by: popovitsj on 11-mrt-2012 5:12

Answer 1

popovitsj wrote:
For my application I need a function that converts a date to a date that is a monday.
I wrote this simple function, and I've been trying for many many times... but it just doesn't work. It returns a null value. The problem lies with the IF-statement.
I'm using iSQL 9
CREATE OR REPLACE FUNCTION to_monday ( datum IN DATE )
RETURN DATE
AS
BEGIN
FOR n IN 0..6 LOOP
IF ( TO_CHAR(datum + n, 'day') = 'friday' ) THEN
RETURN (datum + n - 4);
END IF;
END LOOP;
END;
SELECT to_monday(CURRENT_DATE) FROM dual;Edited by: popovitsj on 11-mrt-2012 5:07
Edited by: popovitsj on 11-mrt-2012 5:09
Edited by: popovitsj on 11-mrt-2012 5:09
Edited by: popovitsj on 11-mrt-2012 5:12You have to use format modifier. to_char(...,'day') will return "friday" with padded space. You have to use to_char(..,'fmday').
SQL> CREATE OR REPLACE FUNCTION to_monday ( datum IN DATE )
  2    RETURN DATE
  3    AS
  4  BEGIN
  5    FOR n IN 0..6 LOOP
  6      IF ( TO_CHAR(datum + n, 'fmday') = 'friday' ) THEN
  7        RETURN (datum + n - 4);
  8      END IF;
  9    END LOOP;
10  END;
11  /
Function created.
SQL> SELECT to_monday(sysdate) from dual;
TO_MONDAY
12-MAR-12