SQL - UPDATE 中每个 SET 命令的 WHERE 子句? [英] SQL - WHERE clause on each SET command in UPDATE?

问题描述

我正在尝试在 PHP 中创建 SQL 查询以更新表.是否可以为每个受影响的行使用不同的 WHERE 子句?

I'm trying to create an SQL query in PHP to update a table. Is it possible to have a different WHERE clause for each affected row?

例如:

UPDATE table 
SET val=X WHERE someproperty = 1,
SET val=Y WHERE someproperty = 2

等等?

任何帮助表示赞赏.谢谢

Any help appreciated. Thanks

推荐答案

对于任何 SQL 语句，您不能有多个 WHERE 子句，但是您可以使用 CASE 语句来完成您想要执行的操作.另一个选项是执行多个 UPDATE 语句.

You cannot have multiple WHERE clauses for any SQL statement, however you can use a CASE statement to accomplish what you are trying to do. Another option that you have is to execute multiple UPDATE statements.

以下是使用 CASE 语句的示例:

Here is a sample using the CASE statement:

UPDATE table
SET val = (
    CASE someproperty
        WHEN 1 THEN X
        WHEN 2 THEN Y
        ELSE val
    END
);

以下是使用多个 UPDATE 语句的示例:

Here is a sample using multiple UPDATE statements:

UPDATE table SET val=X WHERE someproperty = 1;
UPDATE table SET val=Y WHERE someproperty = 2;

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