MySQL查询更新具有相同值的每个替代行字符串？
让我们首先创建一个表-
mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Subject varchar(100) -> );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(Subject) values('C');
mysql> insert into DemoTable(Subject) values('MongoDB');
mysql> insert into DemoTable(Subject) values('Java');
mysql> insert into DemoTable(Subject) values('MongoDB');
mysql> insert into DemoTable(Subject) values('Python');
mysql> insert into DemoTable(Subject) values('MongoDB');使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
输出结果
+----+---------+ | Id | Subject | +----+---------+ | 1 | C | | 2 | MongoDB | | 3 | Java | | 4 | MongoDB | | 5 | Python | | 6 | MongoDB | +----+---------+ 6 rows in set (0.00 sec)
这是每隔第二行字符串更新的查询-
mysql> update DemoTable set Subject=replace(Subject,'MongoDB','MySQL') where Id%2=0; Rows matched: 3 Changed: 3 Warnings: 0
让我们检查表中的所有记录-
mysql> select *from DemoTable;
输出结果
+----+---------+ | Id | Subject | +----+---------+ | 1 | C | | 2 | MySQL | | 3 | Java | | 4 | MySQL | | 5 | Python | | 6 | MySQL | +----+---------+ 6 rows in set (0.00 sec)