Informix Error -301

Reasons / Common Causes

-301 is the byte-size sibling of -300's column-count limit: even with an acceptable number of GROUP BY columns, their combined byte width can't exceed the server's implementation limit — every server supports at least 120 bytes total. Wide character columns are the usual culprit, since a handful of them can exhaust the budget well before hitting the column-count limit.

1. A GROUP BY clause listing a small number of columns, but wide ones — several VARCHAR/CHAR columns of significant declared length combined can exceed 120 bytes even with just two or three columns.
2. Grouping by columns wider than actually needed to distinguish groups — e.g. a long description or comment column included in GROUP BY when only its identifier is needed.
3. Schema growth — column widths increased over time (a VARCHAR(20) widened to VARCHAR(100)), pushing a previously-fine GROUP BY clause over the limit without the query itself changing.

Solutions / Resolution

1. Reduce the total byte width of the GROUP BY columns, per the official guidance — group by narrower identifying columns instead of wide descriptive ones where possible.
2. See -300's staged restructuring approach if the query genuinely needs to distinguish rows by wide columns: group by narrow essential columns into a temp table, then join back to retrieve the wide columns afterward.
3. Check for a recent column-width increase if a previously-working query starts failing — the query didn't change, but the underlying schema did.

Examples

Wide columns exceeding the byte budget

SELECT customer_name, shipping_address, billing_address, COUNT(*)
FROM orders
GROUP BY customer_name, shipping_address, billing_address;
-- -301: three VARCHAR(100)-class columns together exceed the
-- combined GROUP BY byte limit

Fix — group by a narrow identifying column instead, then join back for the wide ones:

SELECT customer_id, COUNT(*) AS cnt
INTO TEMP grouped_orders
FROM orders
GROUP BY customer_id;

SELECT o.customer_name, o.shipping_address, o.billing_address, g.cnt
FROM grouped_orders g, orders o
WHERE g.customer_id = o.customer_id;

Diagnostic Checks

1. Sum the declared widths of every column in the GROUP BY clause and compare against the server's documented byte limit (at least 120 bytes).
2. Check for a recent widening of any grouped column's data type if a query that used to work started failing without any query changes.

Related Errors / Related Topics

• -300 — "There are too many GROUP BY columns." The column-count sibling of this byte-size limit — see its addendum for the staged temp-table-and-join restructuring pattern, which applies equally here.
• -294 — "The column column-name must be in the GROUP BY list." The general GROUP BY-membership requirement this limit sits alongside.

Group by narrow identifying columns and join back for wide descriptive ones — the same restructuring pattern used for -300 resolves this byte-size limit too.