如何使用条件替换MySQL表中的行?

使用MySQL CASE语句来设置条件和替换行。让我们先创建一个表 –

mysql> create table DemoTable1481
      -> (
      -> PlayerScore int
      -> );
Query OK, 0 rows affected (0.42 sec)

使用insert命令向表中插入一些记录 –

mysql> insert into DemoTable1481 values(454);
Query OK, 1 row affected (0.41 sec)
mysql> insert into DemoTable1481 values(765);
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable1481 values(890);
Query OK, 1 row affected (0.09 sec)

使用select语句显示表中的所有记录 –

mysql> select * from DemoTable1481;

这将产生以下输出 –

+-------------+
| PlayerScore |
+-------------+
|        454 |
|        765 |
|        890 |
+-------------+
3 rows in set (0.00 sec)

以下是在MySQL表中替换行的查询 –

mysql> update DemoTable1481
      -> set PlayerScore= case when PlayerScore=454 then 1256
      -> when PlayerScore=765 then 1865
      -> when PlayerScore=890 then 3990
      -> end
      -> ;
Query OK, 3 rows affected (0.17 sec)
Rows matched: 3  Changed: 3 Warnings: 0

让我们再次检查表记录 –

mysql> select * from DemoTable1481;

这将产生以下输出 –

+-------------+
| PlayerScore |
+-------------+
|        1256 |
|        1865 |
|        3990 |
+-------------+
3 rows in set (0.00 sec)

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