Sql的查询索引怎么做?
请问下面这个查询语句的索引怎么做呢?数据量50000条左右查询很慢。
select a.*,b.CardClassName,c.UserName,d.AgentName from Card a
left join CardClass b on a.CardClassID=b.CardClassID
left join Users c on a.UserID = c.UserID
left join Agents d on a.AgentID = d.AgentID
先说声谢谢啦!!!