Question

我有一个使用新数据更新现有记录所需的存储过程，但它不能“覆盖”任何现有数据。

例如，我们可能有三个字段：

 FirstName | LastName | PhoneNumber

调用上面的'TableX'。

在一个非常简单的更新中，这看起来像这样：

 Update TableX
 set    FirstName = [TableY.FirstName]
       ,LastName = [TableY.LastName]
       ,PhoneNumber = [TableY.PhoneNumer]
 etc.....

但是我要求每列只有更新（来自TableY），如果它是空的。

Answer 1

Update TableX
set    FirstName = ISNULL(FirstName, [TableY.FirstName])
      ,LastName = ISNULL(LastNastName, [TableY.LastName])
      ,PhoneNumber = ISNULL(PhoneNumber, [TableY.PhoneNumer])

...

如果'empty'不代表NULL，那么

Update TableX
set    FirstName = case FirstName when "" then [TableY.FirstName] else FirstName end
      ,LastName = case LastName when "" then [TableY.LastName]) else LastName end
      ,PhoneNumber = case PhoneNumber when "" then [TableY.PhoneNumer] else PhoneNumber end

Answer 2

您需要使用when then来执行此操作。

UPDATE [AdventureWorks_DB].[dbo].[activities]
SET  [FirstName ] = case  when FirstName  is  null then 'pass First Name'
                     else  [FirstName ]
end,
LastName  = case  when LastName  is  null then 'pass Last Name'
          else  LastName 
end,
PhoneNumber = case  when PhoneNumber is  null then 'pass PhoneNumber'
        else  PhoneNumber
end

Answer 3

update
    TableX
set 
FirstName = (case when FirstName = null then  @firstname else FirstName end)
where 
Id=1

Answer 4

因为更新在逻辑上是删除，所以插入对使用COALESCE模式没有任何害处，尽管最好不要检查所有NULL参数值，例如

UPDATE TableX
   SET FirstName = COALESCE(@FirstName, FirstName), 
       LastName = COALESCE(@LastName, LastName), 
       PhoneNumber = COALESCE(@PhoneNumber, PhoneNumer)
 WHERE COALESCE(@FirstName, @LastName, @PhoneNumber) IS NOT NULL
       AND person_X_ID = @person_X_ID;

有选择地更新字段

4 个答案: