TSQL 条件 IS NULL 和 = 运算符
我想在一份声明中写下这一点,该怎么做?
-- Is there a block for this user?
SELECT @BlockID = BlockID FROM [Blocks]
WHERE UserID = @UserID
-- If not exists, get the default one
IF @BlockID IS NULL
SELECT @BlockID = BlockID FROM [Blocks]
WHERE UserID IS NULL
I am trying to write this in one statement, how to do this?
-- Is there a block for this user?
SELECT @BlockID = BlockID FROM [Blocks]
WHERE UserID = @UserID
-- If not exists, get the default one
IF @BlockID IS NULL
SELECT @BlockID = BlockID FROM [Blocks]
WHERE UserID IS NULL
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合并
。它还可以轻松扩展到两个以上的情况。coalesce
. It also expands to more than two cases easily.