仅当它存在于mysql服务器5.0中时，删除约束 [英] Drop constraints only if it exists in mysql server 5.0

问题描述

我想知道仅在存在约束的情况下如何删除它. mysql服务器中是否存在任何单行语句，这将允许我执行此操作.

i want to know how to drop a constraint only if it exists. is there any single line statement present in mysql server which will allow me to do this.

我尝试了以下命令，但无法获得期望的输出

i have tried the following command but unable to get the desire output

alter table airlines 
drop foreign key if exits FK_airlines;

对此的任何帮助确实帮助我在mysql中前进

any help to this really help me to go forward in mysql

推荐答案

除非您愿意检测错误并继续操作(而不是不好的事情.)

I do not believe this is possible in a single line, unless you are willing to detect the error and move on (not a bad thing).

INFORMATION_SCHEMA数据库包含您需要告知外键是否存在的信息，因此您可以分两步实施.

The INFORMATION_SCHEMA database contains the info you need to tell if the foreign key exists, so you could implement it in a 2 step process.

http://dev.mysql.com/doc/refman/5.1/en/table-constraints-table.html

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