When inserting invalid values into a DATE column, some subsequent SELECTs may print the following warning:

Warning 1292 Incorrect date value: '0000-00-00 00:00:00.000001' for column 'f1' at row 1

even though no such value is present in the table.

Test case:

CREATE TABLE t1 (f1 DATE NOT NULL, KEY (f1));

INSERT INTO t1 VALUES (2006),('02:55:59');

SELECT f1 FROM t1 FORCE KEY (f1) WHERE f1 NOT IN ( '2001-05-09' , STR_TO_DATE (CURDATE(), 'bogus') );

SHOW WARNINGS;