Informix Error -660

Reasons / Common Causes

-660 fires when a FOR statement's loop variable is assigned a new value inside the loop body — per the official guidance, loop variables are managed by the FOR statement itself and can't be modified from within.

1. A LET statement inside a FOR loop assigning directly to the loop variable, per the official guidance — the direct, only cause.
2. An attempt to skip iterations or change the loop's direction by manipulating the loop variable's value mid-loop, a pattern that works in some general-purpose languages but isn't supported here.

Solutions / Resolution

1. Use a different variable in the LET statement, per the official guidance's documented correction, rather than modifying the loop variable directly.
2. If early termination or a skip is genuinely needed, use EXIT FOR/CONTINUE FOR to control the loop's flow instead of trying to alter the loop variable's value.

Examples

The disallowed attempt

FOR i = 1 TO 10
  LET i = i + 5;  -- -660: i is the loop variable
  ...
END FOR;

Corrected — use a separate variable

DEFINE v_adjusted INT;
FOR i = 1 TO 10
  LET v_adjusted = i + 5;
  ...
END FOR;

Or corrected — use EXIT FOR to change flow instead

FOR i = 1 TO 10
  IF some_condition THEN
    EXIT FOR;
  END IF;
  ...
END FOR;

Diagnostic Checks

1. Scan LET statements inside FOR loop bodies for an assignment to the loop variable itself, and redirect it to a separate variable.

Related Errors / Related Topics

• -662 — "Loop variable variable-name specified more than once." A related FOREACH/loop- variable restriction, about reusing a variable name rather than modifying it inside the loop.

Loop variables are managed entirely by the FOR statement — assign to a separate variable, or use EXIT FOR/CONTINUE FOR to control flow instead.