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我们可以借助 ALTER TABLE 语句将 NOT NULL 约束应用于现有 MySQL 表的列。 语法ALTER TABLE table_name MODIFY colum_name datatype NOT NULL; 登录后复制 示例mysql> Create table test123(ID INT, Date DATE);
Query OK, 0 rows affected (0.19 sec)
mysql> Describe test123;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| ID | int(11) | YES | | NULL | |
| Date | date | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.04 sec)
mysql> ALTER TABLE test123 MODIFY ID INT NOT NULL;
Query OK, 0 rows affected (0.54 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> Describe test123;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| ID | int(11) | NO | | NULL | |
| Date | date | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.06 sec) 登录后复制 |
