Informix Error -697

Reasons / Common Causes

-697 fires when a FOR statement's STEP expression evaluates to zero — per the official guidance's example, LET e = -1; FOR i = 10 TO 20 STEP e+1 computes a step of -1 + 1 = 0, which would never advance the loop variable at all.

1. A STEP expression built from variables whose combined value happens to be zero, per the official guidance's example — not obviously zero from the literal syntax, only after evaluation.
2. A STEP expression that's correct in most cases but degenerates to zero for certain input values, surfacing only under specific runtime conditions rather than every time the routine runs.

Solutions / Resolution

1. Change the STEP expression so it evaluates to a nonzero value, per the official guidance's documented correction.
2. If the STEP expression is built from variables, trace their values at the point of failure to understand why the combination produced zero this time.
3. Add a guard before the FOR statement if the step is computed from data that could legitimately produce zero, handling that case explicitly rather than letting it reach the loop.

Examples

The disallowed zero step

DEFINE e INT;
LET e = -1;
FOR i = 10 TO 20 STEP e + 1
  ...
END FOR;
-- -697: e + 1 evaluates to 0

Corrected

DEFINE e INT;
LET e = -1;
FOR i = 10 TO 20 STEP e + 2
  ...
END FOR;

Diagnostic Checks

1. Evaluate the STEP expression's actual computed value, not just its literal syntax, since a zero result can come from a combination of variables that isn't obviously zero at a glance.

Related Errors / Related Topics

• -683 — "Specified STEP expression will not traverse RANGE." A related FOR-loop STEP error, about the step's sign being wrong for the range's direction, rather than the step being exactly zero.

A zero step is a distinct failure from -683's wrong-direction step — check the expression's actual evaluated value, not just its literal form.