Informix Error -443

Reasons / Common Causes

-443 fires in a stored procedure's FOR loop when one of its three range parameters — start value, end value, or step value — evaluates to NULL. All three need concrete numeric values for the loop to be well-defined; a NULL bound or step has no sensible iteration meaning.

1. A FOR loop range expression referencing a column or variable that's currently NULL — the most common cause, especially when the bound comes from a query result that could return no matching value.
2. An uninitialized stored-procedure variable used as a range bound, defaulting to NULL before being explicitly set.
3. A step value expression that evaluates to NULL under some input combination not anticipated when the procedure was written.

Solutions / Resolution

1. Ensure all three range parameters (start, end, step) evaluate to concrete numeric values, per the official guidance, before the FOR loop executes.
2. Add a NULL check (or a default via NVL/COALESCE-equivalent logic) on any range parameter sourced from a query result or variable that might not always be populated.
3. Initialize stored-procedure variables explicitly before using them as range bounds, rather than relying on their default value.

Examples

A NULL end value from a query result

CREATE PROCEDURE process_range()
DEFINE max_id INTEGER;
    SELECT MAX(order_id) INTO max_id FROM orders WHERE status = 'archived';
    -- if no rows match, max_id is NULL here
    FOR i = 1 TO max_id
        -- -443 if max_id is NULL
    END FOR
END PROCEDURE;

Fix — guard against a NULL bound:

CREATE PROCEDURE process_range()
DEFINE max_id INTEGER;
    SELECT MAX(order_id) INTO max_id FROM orders WHERE status = 'archived';
    IF max_id IS NULL THEN
        RETURN;
    END IF;
    FOR i = 1 TO max_id
        -- safe to iterate now
    END FOR
END PROCEDURE;

Diagnostic Checks

1. Check each of the three range parameters (start, end, step) for a possible NULL source.
2. Trace back to where a NULL range parameter originates — an unmatched query, an uninitialized variable, or an unexpected input combination.

Related Errors / Related Topics

• -391 — "Cannot insert a null into column column-name." A related NULL-handling discipline, in the context of table columns rather than stored-procedure loop bounds.

Guard against a NULL range bound explicitly before entering a FOR loop, especially when a bound comes from a query result that might not match any rows.