方法二：通过工具
用pt-duplicate-key-checker 工具检查重复及冗余索引 使用方法 pt-duplicate-key-checker -hxxx -uxxx -pxxx
查找重复与冗余索引
参考慕课网：http://www.imooc.com/video/3998
MySQL索引的维护与优化——查找重复及冗余索引
标签：select 使用方法 weight 使用 seq rom sele dup index
MySQL索引的维护与优化——查找重复及冗余索引
a.table_schema AS ‘数据库‘, a.table_name AS ‘表名‘, a.index_name AS ‘索引1‘, b.index_name AS ‘索引2‘, a.column_name AS ‘重复列名‘
FROM information_schema.statistics a
JOIN statistics b ON a.table_schema = b.table_schema
AND a.table_name = b.table_name
AND a.seq_in_index = b.seq_in_index
AND a.column_name = b.column_name
WHERE a.seq_in_index = 1
AND a.index_name != b.index_name