Question

我想用其他列更新列...

我的代码：

update Table1 set Table1.number = Table2.number from Table1 where Table2.Table1Id= Table1.id;

错误：

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'from Table1 where Table2.Table1Id= Table1.id' at line 1

Answer 1

执行此更新的ANSI方法是：

UPDATE Table1 
SET     Table1.number = (   SELECT  Table2.number
                            FROM    Table2
                            WHERE   Table2.Table1Id= Table1.id
                        )
WHERE   EXISTS
        (   SELECT  Table2.number
            FROM    Table2
            WHERE   Table2.Table1Id= Table1.id
        );

或者专有的MySQL UPDATE / JOIN语法是：

UPDATE  Table1 
        INNER JOIN Table2
            ON Table2.Table1Id= Table1.id;
SET     Table1.number = Table2.number;

这里的ANSI语法很差，特别是如果你需要更新多个字段，例如：

UPDATE Table1 
SET     Table1.number = (   SELECT  Table2.number
                            FROM    Table2
                            WHERE   Table2.Table1Id= Table1.id
                        ),
        Table1.number2 = (  SELECT  Table2.number2
                            FROM    Table2
                            WHERE   Table2.Table1Id= Table1.id
                        ),
        Table1.number3 = (  SELECT  Table2.number3
                            FROM    Table2
                            WHERE   Table2.Table1Id= Table1.id
                        )
WHERE   EXISTS
        (   SELECT  Table2.number
            FROM    Table2
            WHERE   Table2.Table1Id= Table1.id
        );

我认为即使是那些坚持使用ANSI兼容代码的人中最坚定的也很难通过一个简单的连接为此做好准备！

Answer 2

在MySQL中，您可以在join：

中使用update

update Table1 join
       Table2
       on Table2.Table1Id = Table1.id
    set Table1.number = Table2.number ;

这似乎是您的语法意图。

使用其他列进行更新

2 个答案: