Sql 如果更新查询影响多行，则跳过该查询

可能重复：

我在SQLServer2005中有一个更新查询

update custom_graphics_files 
set actual_file_Name = @CorrectName 
where actual_file_Name = @FileName

---

现在，如果有多个

实际的\u文件名

，我想跳过更新查询，

我喜欢为此使用窗口函数：

update t
set t.actual_file_Name = @CorrectName 
FROM custom_graphics_files t
INNER JOIN
(
   SELECT actual_file_Name, COUNT(*) TheCount
   FROM custom_graphics_files 
   GROUP BY actual_file_Name
) t2 ON t.actual_file_Name = t2.actual_file_Name AND TheCount = 1
where t.actual_file_Name = @FileName;

with toupdate as (
      select cgf.*, COUNT(*) over (PARTITION by actual_file_name) as ActCnt
      from custom_graphics_files
     )
update toupdate
    set actual_file_Name = @CorrectName 
    where actual_file_Name = @FileName and ActCnt = 1

在大型表上，这可能不是最有效的解决方案，这取决于

actual\u file\u Name=@FileName

的选择性。这是您可以得到的最“可读”的查询：

update custom_graphics_files 
set actual_file_Name = @CorrectName 
where actual_file_Name = @FileName
and (select count(1) from custom_graphics_files where actual_file_Name = @FileName) = 1