SELECT/ UPDATE RETURNING INTO a single row-field fails with ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT, even though the column count matches

CREATE TABLE t1 (a INT, b VARCHAR(10));

INSERT INTO t1 VALUES (10,'b10');

DELIMITER $$;

CREATE PROCEDURE p1()

BEGIN

  DECLARE r0 ROW (a INT, b VARCHAR(10));

  SELECT a INTO r0.a FROM t1;

  SELECT r0.a;

END;

$$

DELIMITER ;$$

--error ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT

CALL p1;

DROP PROCEDURE p1;

DELIMITER $$;

CREATE PROCEDURE p2()

BEGIN

  DECLARE r0 ROW (a INT, b VARCHAR(10));

  UPDATE t1 SET a=a+1 RETURNING a INTO r0.a;

  SELECT r0.a;

END;

$$

DELIMITER ;$$

--error ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT

CALL p2;

DROP PROCEDURE p2;

DROP TABLE t1;

CREATE TABLE t1 (a INT, b VARCHAR(10));

INSERT INTO t1 VALUES (10,'b10');

CREATE PROCEDURE p1()

BEGIN

DECLARE r0 ROW (a INT, b VARCHAR(10));

SELECT a INTO r0.a FROM t1;

SELECT r0.a;

END;

$$

CALL p1;

ERROR 21000: The used SELECT statements have a different number of columns

DROP PROCEDURE p1;

CREATE PROCEDURE p2()

BEGIN

DECLARE r0 ROW (a INT, b VARCHAR(10));

UPDATE t1 SET a=a+1 RETURNING a INTO r0.a;

SELECT r0.a;

END;

$$

CALL p2;

ERROR 21000: The used SELECT statements have a different number of columns