组合两个SQL select语句需要30到40分钟才能执行

Question

RDBMS-MS SQL

如何将这两个SQL选择查询合并为一个并快速执行它们：

查询1

select 
VVO.VV_CODE, 
V.Vessel_name,                       
VVO.Arrival_date, 
isnull(IGM.VIR_NO,'NULL') as VIR_NO,
isnull(VVO.TERMINAL_CODE,'NULL') as TERMINAL_CODE
from Vessel_voyage VVO, Vessel V, IGM 
where V.Vessel_code = substring(VVO.VV_CODE,1,3) and VVO.VV_CODE = IGM.VV_CODE

查询2

select
BLD.BL_NO,                          
isnull(BLD.Parent_BL,'NULL') as Parent_BL,  
BLD.Consignee_Description,
DO.DO_Issue_Date,                   
CA.CAgent_Name,                     
BLC.Container_No ,                  
CS.Container_Size_Description           
from BL_DATA BLD, CAgent CA, Delivery_Order DO, BL_Container BLC, Container_Size CS 
where BLD.BL_NO = DO.BL_NO and DO.CAgent_Code = CA.CAgent_Code and BLD.BL_NO = BLC.BL_NO and BLC.Container_Size_Code = CS.Container_Size_Code

分别执行这些选择查询，它们将在几秒钟内被执行。

但是将它们变成单个选择查询，它们大约需要30到40分钟才能被执行。

这是我尝试过的：

select 
VVO.VV_CODE, 
V.Vessel_name,                       
VVO.Arrival_date, 
isnull(IGM.VIR_NO,'NULL') as VIR_NO,
isnull(VVO.TERMINAL_CODE,'NULL') as TERMINAL_CODE,
BLD.BL_NO,                          
isnull(BLD.Parent_BL,'NULL') as Parent_BL,  
BLD.Consignee_Description,
DO.DO_Issue_Date,                   
CA.CAgent_Name,                     
BLC.Container_No ,                  
CS.Container_Size_Description       
from Vessel_voyage VVO, Vessel V, IGM ,BL_DATA BLD, CAgent CA, Delivery_Order DO, BL_Container BLC, Container_Size CS 
where V.Vessel_code = substring(VVO.VV_CODE,1,3) and VVO.VV_CODE = IGM.VV_CODE and BLD.BL_NO = DO.BL_NO and DO.CAgent_Code = CA.CAgent_Code and BLD.BL_NO = BLC.BL_NO and BLC.Container_Size_Code = CS.Container_Size_Code

Answer 1

使用ANSI样式联接编写查询将使其更易于阅读-因此我已经做到了。它还有助于发现联接逻辑中存在问题的地方。

重新编写我得到的联接：

from Vessel_voyage VVO
inner join Vessel V on V.Vessel_code = substring(VVO.VV_CODE,1,3)
inner join IGM on VVO.VV_CODE = IGM.VV_CODE
inner join BL_DATA BLD on BLD.BL_NO = DO.BL_NO
inner join CAgent CA
inner join Delivery_Order DO on DO.CAgent_Code = CA.CAgent_Code
inner join BL_Container BLC on BLD.BL_NO = BLC.BL_NO
inner join Container_Size CS on BLC.Container_Size_Code = CS.Container_Size_Code

我可以绕着DO到CA联接谓词移动，但最终我有8个表联接，但是只有6个谓词联接它们-最终结果是，其中一个表是笛卡尔运算，可能会给出错误的结果，但肯定会导致性能下降。

如果您使用这种连接方式，我怀疑您将能够很轻松地对其进行修复。