记一次简单的sql优化

select round(sum(qj0109)/10000,1) from qylist where sfmsqx='y' and lybmhy!=''；

进行优化

select round(sum(b.qj0109)/10000,1) from (select a.qj0109 from qylist a where  a.sfmsqx='y' and a.lybmhy!='') b