Transact-sql中的条件运算符

Question

有没有办法做到这一点较短，例如在Transact-sql中使用某种条件运算符？

IF @ParentBinaryAssetStructureId = -1 
BEGIN 
    SET @ParentBinaryAssetStructureId = NULL 
END 

UPDATE BinaryAssets.BinaryAssetStructures 
SET  ParentBinaryAssetStructureId = @ParentBinaryAssetStructureId 
WHERE BinaryAssetStructureId = @OriginalBinaryAssetStructureId 

Answer 1

使用NULLIF()

UPDATE BinaryAssets.BinaryAssetStructures 
SET  ParentBinaryAssetStructureId = NULLIF(@ParentBinaryAssetStructureId,-1) 
WHERE BinaryAssetStructureId = @OriginalBinaryAssetStructureId 

Answer 2

UPDATE BinaryAssets.BinaryAssetStructures 
SET  ParentBinaryAssetStructureId = 
    CASE ParentBinaryAssetStructureId 
    WHEN -1 THEN NULL 
    ELSE ParentBinaryAssetStructureId 
    END 
WHERE BinaryAssetStructureId = @OriginalBinaryAssetStructureId 

给一个抡

Answer 3

三元（条件）运算符在C一样的语言：

x = doSomething ? 5 : 7 

会这样写在SQL中：

SELECT @x = CASE WHEN @doSomething = 1 THEN 5 ELSE 0 END 

可以有多个的情况下（当子句）：

SELECT @x = CASE WHEN @doSomething = 1 THEN 5 WHEN @somethingElse = 1 THEN 20 ELSE 0 END