MySQL 将空白值列更新为 NULL
mysqlmysqli database更新于 2024/8/11 9:48:17
为此，您可以将 IF() 与 UPDATE 命令一起使用。让我们首先创建一个表 −
mysql> create table DemoTable1601 -> ( -> FirstName varchar(20) , -> LastName varchar(20) -> ); Query OK, 0 rows affected (0.53 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable1601 values('John','Doe');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable1601 values('Adam','');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable1601 values('David','Miller');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable1601 values('Chris','');
Query OK, 1 row affected (0.11 sec)
使用 select 语句显示表中的所有记录 −
mysql> select * from DemoTable1601;
这将产生以下输出 −
+-----------+----------+ | FirstName | LastName | +-----------+----------+ | John | Doe | | Adam | | | David | Miller | | Chris | | +-----------+----------+ 4 rows in set (0.00 sec)
以下是将列更新为空或其值的查询 −
mysql> update DemoTable1601 set LastName=if(LastName='',NULL,LastName); Query OK, 2 rows affected (0.22 sec) Rows matched: 4 Changed: 2 Warnings: 0
让我们再次检查表记录 −
mysql> select * from DemoTable1601;
这将产生以下输出 −
+-----------+----------+ | FirstName | LastName | +-----------+----------+ | John | Doe | | Adam | NULL | | David | Miller | | Chris | NULL | +-----------+----------+ 4 rows in set (0.00 sec)
相关文章
有用资源
mysql 参考教程 - 该教程包含有关 mysql 的更多信息:https://www.cainiaomax.com/mysql/
