SELECT produces more warnings in non-strict mode than in strict mode

SET NAMES utf8;

SET collation_connection=big5_chinese_ci;

CREATE TABLE t1 (b VARCHAR(2));

INSERT INTO t1 VALUES ('0'),('1'),('2'),('3'),('4'),('5'),('6'),('7');

INSERT INTO t1 VALUES ('8'),('9'),('A'),('B'),('C'),('D'),('E'),('F');

CREATE TEMPORARY TABLE head AS SELECT concat(b1.b, b2.b) AS head FROM t1 b1, t1 b2;

CREATE TEMPORARY TABLE tail AS SELECT concat(b1.b, b2.b) AS tail FROM t1 b1, t1 b2;

DROP TABLE t1;

CREATE TABLE t1 AS

SELECT concat(head, tail) AS code, ' ' AS a

FROM head, tail

WHERE (head BETWEEN '80' AND 'FF') AND (tail BETWEEN '20' AND 'FF')

ORDER BY head, tail;

DROP TEMPORARY TABLE head, tail;

UPDATE IGNORE t1 SET a=unhex(code) ORDER BY code;

set sql_mode='';

SELECT * FROM t1

WHERE HEX(CAST(LOWER(a) AS CHAR CHARACTER SET utf8)) <>

HEX(LOWER(CAST(a AS CHAR CHARACTER SET utf8))) ORDER BY code;

+------+-----+

| code | a   |

+------+-----+

| A2B9 | Ⅰ   |

| A2BA | Ⅱ   |

| A2BB | Ⅲ   |

| A2BC | Ⅳ   |

| A2BD | Ⅴ   |

| A2BE | Ⅵ   |

| A2BF | Ⅶ   |

| A2C0 | Ⅷ   |

| A2C1 | Ⅸ   |

| A2C2 | Ⅹ   |

+------+-----+

10 rows in set, 512 warnings (0.45 sec)

MariaDB [test]> SHOW WARNINGS;

+---------+------+--------------------------------------------------+

| Level   | Code | Message                                          |

+---------+------+--------------------------------------------------+

| Warning | 1977 | Cannot convert 'big5' character 0xA3C0 to 'utf8' |

| Warning | 1977 | Cannot convert 'big5' character 0xA3C0 to 'utf8' |

| Warning | 1977 | Cannot convert 'big5' character 0xA3C1 to 'utf8' |

| Warning | 1977 | Cannot convert 'big5' character 0xA3C1 to 'utf8' |

...

set sql_mode='STRICT_TRANS_TABLES';

SELECT * FROM t1

WHERE HEX(CAST(LOWER(a) AS CHAR CHARACTER SET utf8)) <>

HEX(LOWER(CAST(a AS CHAR CHARACTER SET utf8))) ORDER BY code;

+------+-----+

| code | a   |

+------+-----+

| A2B9 | Ⅰ   |

| A2BA | Ⅱ   |

| A2BB | Ⅲ   |

| A2BC | Ⅳ   |

| A2BD | Ⅴ   |

| A2BE | Ⅵ   |

| A2BF | Ⅶ   |

| A2C0 | Ⅷ   |

| A2C1 | Ⅸ   |

| A2C2 | Ⅹ   |

+------+-----+

10 rows in set, 256 warnings (0.38 sec)

MariaDB [test]> SHOW WARNINGS;

+---------+------+--------------------------------------------------+

| Level   | Code | Message                                          |

+---------+------+--------------------------------------------------+

| Warning | 1977 | Cannot convert 'big5' character 0xA3C0 to 'utf8' |

| Warning | 1977 | Cannot convert 'big5' character 0xA3C1 to 'utf8' |

| Warning | 1977 | Cannot convert 'big5' character 0xA3C2 to 'utf8' |

...