DB查询语句的编写和执行顺序
编写顺序:select,distinct,from,join,on,where,group by,having ,order by , limit
执行顺序: from,on,join,where,group by,having,select,distinct,order by, limit
参考:http://www.jellythink.com/archives/924
参考:http://www.jellythink.com/archives/924