Question

我有一个bit（或int）变量，表示行是否存在。

是的，我知道最好只检查EXISTS，但目前我需要将其设置为我的变量。

所以问题：使用SELECT或EXISTS

更好

DECLARE @signoff int    
set @signoff = 0


Set @signoff = (SELECT TOP 1
    AccountsOperations_ID
    FROM AccountsOperations
    WHERE Operation_ID = 3 and Submission_ID = @SubmissionID and AccountDate is null)

然后检查

if @signoff is null or @signoff = 0

或

DECLARE @signoff bit
    set @signoff = 0

Set @signoff = SELECT CAST(
   CASE WHEN EXISTS(SELECT TOP 1
             AccountsOperations_ID
             FROM AccountsOperations
             WHERE Operation_ID = 3 and Submission_ID = @SubmissionID and AccountDate is null) 
       THEN 1 
   ELSE 
        0 
   END 
AS BIT)

Answer 1

对我来说，就是这样：

DECLARE @signoff bit
    set @signoff = 0

Set @signoff = SELECT CAST(
   CASE WHEN EXISTS(SELECT 1
             FROM AccountsOperations
             WHERE Operation_ID = 3 and Submission_ID = @SubmissionID and AccountDate is null) 
       THEN 1 
   ELSE 
        0 
   END 
AS BIT)

您根本不需要顶部，这可能会导致查询的额外工作。

Answer 2

添加评论：

DECLARE @signoff bit
    set @signoff = 0

IF EXISTS(SELECT 1
             FROM AccountsOperations
             WHERE Operation_ID = 3 and Submission_ID = @SubmissionID and AccountDate is null) 

SELECT @signoff = 1

您不需要TOP或ELSE，因为您无论如何都要将其默认为0.

Answer 3

使用IF EXISTS你可以这样做，如果row存在，则返回true。

    DECLARE @signoff bit


    IF EXISTS
    (
    SELECT 1
           AccountsOperations_ID
    FROM   AccountsOperations
    WHERE  Operation_ID = 3 and Submission_ID = @SubmissionID and AccountDate is null
    ) 
    SET signoff = 1 -- row exists
    ELSE
    SET signoff = 0 -- row doesn't exists

什么更好使用Exists或Select将此值设置为位变量？

3 个答案: