如果新值和舊值相同不要更新其他更新

Question

如何檢測且僅當新舊價值是不同的其他不更新

Update Student 
SET First = @FirstName 
WHERE EmpId = 1 

Answer 1

可以將此條件添加到您的where條款的更新：

UPDATE Student 
SET First = @FirstName 
WHERE First != @FirstName AND EmpId = 1 

編輯：
正如凱文Suchlicki在評論中指出，如果First爲空，null S的關係明確處理：

UPDATE Student 
SET First = @FirstName 
WHERE EmpId = 1 AND ((First != @FirstName) OR 
         (First IS NULL AND @FirstName IS NOT NULL) OR 
         (First IS NOT NULL AND @FirstName IS NULL))