EC
1306
MariaDBerrorstored-procedureshigh confidence

Not allowed to return a result set from a trigger

Production Risk

Low — trigger compilation fails.

What this means

A SELECT statement that would return a result set to the client was used inside a trigger body.

Why it happens
  1. 1Using a bare SELECT inside a trigger
  2. 2Calling a stored procedure that returns a result set from within a trigger
How to reproduce
trigger — this will error
trigger — this will error
CREATE TRIGGER t BEFORE INSERT ON orders FOR EACH ROW BEGIN SELECT * FROM products; END;

expected output

ERROR 1306 (0A000): Not allowed to return a result set from a trigger

Fix

Use SELECT INTO instead

Use SELECT INTO instead
SELECT col INTO @var FROM t WHERE id = NEW.id;

Why this works

Captures the value without returning a result set to the client.

What not to do

✕

Sources
Official documentation ↗

MySQL 8.0 — 1306 ER_SP_BADSTATEMENT

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