MySQL 8.0.26版本升级32版本查询数据为空的解决方案

greatsql> select version();
+-----------+
| version() |
+-----------+
| 8.0.32-24 |
+-----------+
1 row in set (0.00 sec)

greatsql> show create table t_student;
CREATE TABLE `t_student1` (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `age` int NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

greatsql> select * from t_student;
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  1 | abc    |  10 |
|  2 | 汤姆   |  20 |
+----+--------+-----+
2 rows in set (0.08 sec)

greatsql>  select * from (select * from t_student union select * from t_student) temp where name='汤姆';
Empty set, 2 warnings (0.00 sec)
greatsql> show warnings;
+---------+------+-------------------------------------------------------------------------+
| Level   | Code | Message                                                                 |
+---------+------+-------------------------------------------------------------------------+
| Warning | 1300 | Cannot convert string '\xE6\xB1\xA4\xE5\xA7\x86' from utf8mb4 to binary |
| Warning | 1300 | Cannot convert string '\xE6\xB1\xA4\xE5\xA7\x86' from utf8mb4 to binary |
+---------+------+-------------------------------------------------------------------------+
2 rows in set (0.00 sec)
greatsql> select * from (select * from t_student union select * from t_student) temp;
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  1 | abc    |  10 |
|  2 | 汤姆   |  20 |
+----+--------+-----+
2 rows in set (0.00 sec)
greatsql> select * from (select * from t_student union select * from t_student) temp where name='abc';
+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | abc  |  10 |
+----+------+-----+
1 row in set (0.00 sec)

greatsql> set optimizer_switch='derived_condition_pushdown=off';
Query OK, 0 rows affected (0.00 sec)
greatsql> select * from (select * from t_student union select * from t_student) temp where name='汤姆';
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  2 | 汤姆   |  20 |
+----+--------+-----+
1 row in set (0.00 sec)

greatsql> set optimizer_switch='derived_condition_pushdown=on';
Query OK, 0 rows affected (0.00 sec)
greatsql> select * from (select * from t_student union select * from t_student) temp where name='汤姆';
Empty set, 2 warnings (0.00 sec)
greatsql> select  /*+ NO_DERIVED_CONDITION_PUSHDOWN(temp) */ * from (select * from t_student union select * from t_student) temp where name='汤姆';
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  2 | 汤姆   |  20 |
+----+--------+-----+
1 row in set (0.00 sec)