用一条语句更新表中的许多行？

一尘不染

用一条语句更新表中的许多行？

mysql

更新表中多行的最简单方法是什么？我有一个如下所示的 csv 文件：

|primary_key |value|
|          1 |  xyz|
|          2 |  abc|
|          3 |  def|
...

目标表中已存在具有这些主键的行

我想用这些值更新目标表。是否有语法，以便我可以编写如下内容：

update mytable set value = ('xyz', 'abc', 'def') where primary key = (1,2,3);

阅读 93

2022-10-17

共1个答案

一尘不染

首先是样本数据

mysql> drop table if exists mytable;
Query OK, 0 rows affected (0.03 sec)

mysql> create table mytable
    -> (
    ->     id int not null,
    ->     value VARCHAR(255),
    ->     primary key (id)
    -> );
Query OK, 0 rows affected (0.06 sec)

mysql> insert into mytable (id) values (1),(2),(3);
Query OK, 3 rows affected (0.06 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from mytable;
+----+-------+
| id | value |
+----+-------+
|  1 | NULL  |
|  2 | NULL  |
|  3 | NULL  |
+----+-------+
3 rows in set (0.00 sec)

mysql>

这是新的查询

update mytable A inner join
(
    SELECT 1 id,'xyz' value UNION
    SELECT 2   ,'abc'       UNION
    SELECT 3   ,'def'

) B USING (id)
SET A.value = B.value;

这是执行的新查询

mysql> update mytable A inner join
    -> (
    ->     SELECT 1 id,'xyz' value UNION
    ->     SELECT 2   ,'abc'       UNION
    ->     SELECT 3   ,'def'
    -> ) B USING (id)
    -> SET A.value = B.value;
Query OK, 0 rows affected (0.06 sec)
Rows matched: 3  Changed: 0  Warnings: 0

mysql> select * from mytable;
+----+-------+
| id | value |
+----+-------+
|  1 | xyz   |
|  2 | abc   |
|  3 | def   |
+----+-------+
3 rows in set (0.00 sec)

mysql>

2022-10-17