Question

我有一个update语句，如下所示：

UPDATE  sessions
SET currentStep      = @currentStep,
    chosenDepartment = @chosenDepartment,
    proposedTimes    = @proposedTimes
WHERE   sessionID = @sessionID
    AND empID = @empID;

我使用相同的存储过程进行多次更新，因为我的流程中的每一步都会获得额外的价值。

我的问题：有没有办法只做到这一点：

chosenDepartment = @chosenDepartment

如果@cosenDepartment实际上包含值？

如果我每次都这样做，如果我没有传递任何内容，它将用空白数据覆盖它。

Answer 1

试试这个：

UPDATE  sessions
SET currentStep      = @currentStep,
    chosenDepartment = CASE WHEN @chosenDepartment IS NOT NULL THEN @chosenDepartment ELSE chosenDepartment END,
    proposedTimes    = @proposedTimes
WHERE   sessionID = @sessionID
    AND empID = @empID;

或者

UPDATE  sessions
SET currentStep      = @currentStep,
    chosenDepartment = COALESCE(@chosenDepartment, chosenDepartment),
    proposedTimes    = @proposedTimes
WHERE   sessionID = @sessionID
    AND empID = @empID;

注意＃1：SQL Server将翻译COALESCE(@chosenDepartment, chosenDepartment) 进入CASE WHEN @chosenDepartment IS NOT NULL THEN @chosenDepartment ELSE chosenDepartment END。

注意＃2：如果你想避免使用NULL @chosenDepartment，但如果你想避免使用空字符串或0进行更新，那么你可以使用NULLIF函数：{{ 1}}或COALESCE(NULLIF(@chosenDepartment,''), chosenDepartment)。

Answer 2

您可以在tsql之前放置if语句，这样如果@chosenDepartment为空，那么tsql就不会运行。

仅当存在值时才使用TSQL Update变量

2 个答案: