检查记录是否存在使用mysql删除它 [英] Check if record exists delete it using mysql

问题描述

我正在使用 MySQL，我想检查记录是否存在，如果存在则删除此记录.

i'm using MySQL and i want to check if a record exists and if it exists delete this record.

我尝试了这个，但它对我不起作用:

i try this but it 's not working for me:

SELECT 'Barcelone' AS City, EXISTS(SELECT 1 FROM mytable WHERE City = 'Barcelone') AS 'exists';

THEN

DELETE FROM mytable
WHERE City = 'Barcelone';

感谢您的帮助.

推荐答案

if 语句只允许在存储过程、存储函数和触发器(在 MySQL 中)中使用.

The if statement is only allowed in stored procedures, stored functions, and triggers (in MySQL).

如果我明白你想要什么，就这样做:

If I understand what you want, just do:

DELETE FROM mytable
WHERE City = 'Barcelone';

没有理由事先检查是否存在.只需删除该行.如果不存在，则没有问题.没有错误.

There is no reason to check for the existence beforehand. Just delete the row. If none exist, no problem. No errors.

出于性能原因，我建议在 mytable(city) 上建立索引.如果您想先检查该行是否存在，那很好，但是对于delete 来说是不必要的.

I would recommend an index on mytable(city) for performance reasons. If you want to check if the row exists first, that is fine, but it is unnecessary for the delete.

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