将三条SQL update语句合并为一条

我可以一次而不是三次运行这三个update语句吗？我只能找到mysql的例子来说明如何做到这一点

update    [NoteAlertLog]
set alertmessage = NULL where alertmessage = ''

update    [NoteAlertLog]
set notes = NULL where cast([notes] as nvarchar(max)) = ''

update    [NoteAlertLog]
set externalnotes = NULL where cast(externalnotes as nvarchar(max)) = ''

我尝试过这样做，但出现语法错误：

update    [NoteAlertLog]
set alertmessage = NULL where alertmessage = ''
,set notes = NULL where cast([filenotes] as nvarchar(max)) = ''
,set externalnotes = NULL where cast(externalnotes as nvarchar(max)) = ''

我试过不使用

设置

：

update    [NoteAlertLog]
set alertmessage = NULL where alertmessage = ''
,notes = NULL where cast([filenotes] as nvarchar(max)) = ''
,externalnotes = NULL where cast(externalnotes as nvarchar(max)) = ''

---

使用

case

表达式：

update    [NoteAlertLog]
set alertmessage = case when alertmessage = '' then NULL else alertmessage end,
    notes = case when cast([notes] as nvarchar(max)) = '' then NULL else notes end,
    externalnotes = case when cast(externalnotes as nvarchar(max)) = '' then NULL else externalnotes end

where alertmessage = ''
   or cast([notes] as nvarchar(max)) = ''
   or cast(externalnotes as nvarchar(max)) = ''

---

where

子句可以跳过，但我会保留它以降低事务大小。

使用

case

表达式：

update    [NoteAlertLog]
set alertmessage = case when alertmessage = '' then NULL else alertmessage end,
    notes = case when cast([notes] as nvarchar(max)) = '' then NULL else notes end,
    externalnotes = case when cast(externalnotes as nvarchar(max)) = '' then NULL else externalnotes end

where alertmessage = ''
   or cast([notes] as nvarchar(max)) = ''
   or cast(externalnotes as nvarchar(max)) = ''

---

where

子句可以跳过，但我会保留它以降低事务大小。

您可以这样做，但三个独立的查询更简单。嗯，好的。这只是为了抑制受影响的

x行出现三次，我必须在存储过程的另一个区域中说明这一点。如果整个更新只有一个计数，则通过设置
NOCOUNT
更容易解决问题。您可以这样做，但三个独立的查询更简单。嗯，好的。这只是为了抑制受影响的
x行出现三次，我必须在存储过程的另一个区域中说明这一点。如果整个更新只有一个计数，则通过设置
NOCOUNT
更容易解决问题。