错误消息MySQL服务器在连接数据库时消失了

Question

下面的代码在某个时候可以正常工作，但是突然出现了错误 “数据库连接失败：MySQL服务器已消失”

Select [PROP],M1,M2,M3 from 

(select Prop,Entry, MX from GA_Financial.dbo.tblSAP left join tblMX on GA_Financial.dbo.tblSAP.MDY = tblMX.Datefield) as Tab1

PIVOT
 (
 sum(entry) for MX in (M1,M2,M3)) as TAb2