Displaying Expressions

You can use the TRACE statement with a quoted string or an expression to display values or comments in the output file. If the expression is not a literal expression, the expression is evaluated before it is written to the output file.

You can use the TRACE statement with an expression even if you used a TRACE OFF statement earlier in a routine. You must first, however, use the SET DEBUG statement to establish a trace output file.

The next example uses a TRACE statement with an expression after using a TRACE OFF statement. The example uses UNIX file naming conventions:

CREATE PROCEDURE tracing ()
   DEFINE i INT;
BEGIN
   ON EXCEPTION IN (1)
   END EXCEPTION; -- do nothing
   SET DEBUG FILE TO '/tmp/foo.trace';
   TRACE OFF;
   TRACE 'Forloop starts';
   FOR i IN (1 TO 1000)
      BEGIN
         TRACE 'FOREACH starts';
         FOREACH SELECT...INTO a FROM t
            IF <some condition> THEN
               RAISE EXCEPTION 1    -- emergency exit
            END IF
         END FOREACH                -- return some value
      END
   END FOR                          -- do something
END; 
END PROCEDURE