有些数据杂揉在一起，我们要将其一列分裂成四列，进行联合查询．如下查询语句，将 B.Rssi这一列分为RssiA，RssiB，RssiC，RssiD四列．使用join关键字进行联合查询．
select a.ID ID ,a.PX PX,a.PY PY,b.Rssi RssiA,c.Rssi RssiB,d.Rssi RssiC,e.Rssi RssiD
from (SELECT BP.ID,SP.PX,SP.PY from StaticPrint as SP , BeaconPrint as BP where BP.ID=SP.ID) a join
(select B.Rssi,BP.ID from Beacon as B,BeaconPrint as BP ,StaticPrint as SP where B.ID = BP.BID1 and BP.ID=SP.ID) b on a.ID=b.ID join
(select B.Rssi,BP.ID from Beacon as B,BeaconPrint as BP ,StaticPrint as SP where B.ID = BP.BID2 and BP.ID=SP.ID) c on a.ID=c.ID join
(select B.Rssi,BP.ID from Beacon as B,BeaconPrint as BP ,StaticPrint as SP where B.ID = BP.BID3 and BP.ID=SP.ID) d on a.ID=d.ID join
(select B.Rssi,BP.ID from Beacon as B,BeaconPrint as BP ,StaticPrint as SP where B.ID = BP.BID4 and BP.ID=SP.ID) e on a.ID=e.ID