僅當非null時更新SQL語句

Question

UPDATE main 
SET main.PCH_2YR = 
(SELECT TOP 1 sub.PCH_2YR FROM [dbGlobalPricingMatrix].[dbo].[tblPCHLookup_Test] sub WHERE 
sub.capid = main.capid AND 
sub.milespa = main.mileage AND 
sub.maintained = main.maintenance AND sub.pch_2yr IS NOT NULL) 
FROM [dbWebsiteLO3-PRICING]..Vehicles_Staging_Data main 

我只想設置值，如果子查詢返回的值不是NULL。我怎樣才能做到這一點？

只有一行匹配條件，但我只想使用它的值，如果它不是NULL。

Answer 1

嘗試查詢象下面這樣：

UPDATE main 
SET main.PCH_2YR =sub.PCH_2YR 
FROM [dbWebsiteLO3-PRICING]..Vehicles_Staging_Data main LEFT JOIN 
[dbGlobalPricingMatrix].[dbo].[tblPCHLookup_Test] sub ON 
sub.capid = main.capid AND 
sub.milespa = main.mileage AND 
sub.maintained = main.maintenance AND sub.pch_2yr IS NOT NULL 
WHERE sub.PCH_2YR is NOT NULL 

Answer 2

你可以只在桌子上，而不是子查詢做一個INNER JOIN。 INNER JOIN s過濾掉其他表中沒有匹配的記錄。

UPDATE main 
SET main.PCH_2YR = sub.PCH_2YR 
FROM [dbWebsiteLO3-PRICING]..Vehicles_Staging_Data main 
INNER JOIN [dbGlobalPricingMatrix].[dbo].[tblPCHLookup_Test] sub 
     ON sub.capid = main.capid 
     AND sub.milespa = main.mileage 
     AND sub.maintained = main.maintenance 
     AND sub.pch_2yr IS NOT NULL