Informix Error -33039: Updates are not allowed in singleton select.

Reasons / Common Causes

-33039 fires when an UPDATE is combined with a SELECT that returns only one row without a FOR UPDATE cursor — per the official guidance, such an UPDATE requires a cursor declared FOR UPDATE.

1. An UPDATE combined with a singleton SELECT, without a FOR UPDATE cursor, per the official guidance — the direct, only cause.

Solutions / Resolution

1. Declare a cursor FOR UPDATE for the SELECT, per the official guidance, consulting the DECLARE/SELECT/UPDATE entries in the IBM Informix Guide to SQL: Syntax.

Examples

An UPDATE tied to a singleton SELECT without FOR UPDATE

SELECT total INTO :amt FROM orders WHERE order_id = 1001;
UPDATE orders SET total = :amt * 2 WHERE order_id = 1001;
-- -33039: the singleton SELECT has no FOR UPDATE cursor

Corrected

DECLARE upd_cur CURSOR FOR
  SELECT total FROM orders WHERE order_id = 1001 FOR UPDATE;
OPEN upd_cur;
FETCH upd_cur INTO :amt;
UPDATE orders SET total = :amt * 2 WHERE CURRENT OF upd_cur;

Diagnostic Checks

1. Check whether the singleton SELECT feeding the UPDATE uses a FOR UPDATE cursor, and add one if missing.

Related Errors / Related Topics

No closely related error codes are cross-referenced for -33039 in this set yet.

An UPDATE was tied to a singleton SELECT without a FOR UPDATE cursor — declare one.