mysql。使用空值更新非空列

Question

mysql> SHOW COLUMNS from users LIKE 'created_at';
+------------+----------+------+-----+---------+-------+
| Field      | Type     | Null | Key | Default | Extra |
+------------+----------+------+-----+---------+-------+
| created_at | datetime | NO   |     | NULL    |       |
+------------+----------+------+-----+---------+-------+
1 row in set (0.00 sec)

mysql> SHOW VARIABLES LIKE 'innodb_strict_mode';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| innodb_strict_mode | ON    |
+--------------------+-------+
1 row in set (0.00 sec)

mysql> UPDATE `users` SET `created_at` = NULL WHERE `users`.`id` = 200;
Query OK, 1 row affected, 1 warning (0.02 sec)
Rows matched: 1  Changed: 1  Warnings: 1

mysql> SELECT `created_at` from `users` WHERE `users`.`id` = 200;
+---------------------+
| created_at          |
+---------------------+
| 0000-00-00 00:00:00 |
+---------------------+
1 row in set (0.00 sec)

这是正常行为吗？只是警告。

Answer 1

是的，这可能是正常行为。这取决于服务器的 SQL 模式。数据库可能未处于严格模式，并且允许零日期。

在此页面上查看更多详细信息 - Server SQL Modes :STRICT_ALL_TABLES，STRICT_TRANS_TABLES，NO_ZERO_DATE。

使用此查询检查当前 SQL 模式 -

SHOW VARIABLES WHERE variable_name = 'sql_mode';