如何使用“if exists”？在MySQL中创建或删除索引？ [英] How can I employ "if exists" for creating or dropping an index in MySQL?

问题描述

我想知道是否有办法在创建索引或在MySQL上销毁它之前检查索引是否存在。几年前似乎有一个功能请求，但我找不到任何解决方案的文档。这需要在使用MDB2的PHP应用程序中完成。

I was wondering if there's a way to check if an index exists before creating it or destroying it on MySQL. It appears that there was a feature request for this a few years back, but I can't find any documentation for a solution. This needs to be done in a PHP app using MDB2.

推荐答案

这是我的4班：

set @exist := (select count(*) from information_schema.statistics where table_name = 'table' and index_name = 'index' and table_schema = database());
set @sqlstmt := if( @exist > 0, 'select ''INFO: Index already exists.''', 'create index i_index on tablename ( columnname )');
PREPARE stmt FROM @sqlstmt;
EXECUTE stmt;

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