使用"UNION [ALL]"命令髓绽，可以實現(xiàn)多條SQL語句結(jié)果的合并
不加"ALL"會在多條結(jié)果中進行去重敛苇，示例：
SELECT AccountID, InstrumentID, PosiDirection, Position FROM `t_FuturePosition` WHERE AccountID = '9099'
UNION ALL
SELECT AccountID, InstrumentID, PosiDirection, Position FROM `t_FuturePosition` WHERE AccountID = '99099'
ORDER BY InstrumentID
