如何在存在条件下执行子查询？

Question

declare @qry varchar(100)
declare @cnt int
set @qry = ' where '

if exists( select * from  ARTICLE_MANAGE +@qry+ article_id=65)
BEGIN
select top 1* from  ARTICLE_MANAGE order by article_id desc
END
ELSE
BEGIN
select * from  ARTICLE_MANAGE order by article_id desc
END

这是查询。 '@qry' 被我们传递给查询的内容改变了

Answer 1

DECLARE @qry VARCHAR(100);
DECLARE @cnt INT;
set @qry = ' where '
DECLARE @ExeQuery VARCHAR(MAX);
SET @ExeQuery='if exists( select * from  ARTICLE_MANAGE '+@qry+' article_id=65)
BEGIN
select top 1* from  ARTICLE_MANAGE order by article_id desc
END
ELSE
BEGIN
select * from  ARTICLE_MANAGE order by article_id desc
END'
 EXEC(@ExeQuery)

Answer 2

您在这里构建了一个 dynamic sql 和 EXISTS 限制，仅 subquery。

您可以通过 count(*)

获得 EXISTS 的功能

declare @qry varchar(100) 
declare @cnt int 
set @qry = ' where '

declare @sql_qry nvarchar(1000) 
set @sql_qry = 'select @Cnt = COUNT(*) from  ARTICLE_MANAGE' + @qry + 'article_id=65'

DECLARE @Count AS INT
EXEC sp_executesql @Query, N'@Cnt INT OUTPUT', @Cnt=@Count OUTPUT

if exists(@Count > 0) BEGIN
    select top 1* from  ARTICLE_MANAGE order by article_id desc
END
ELSE BEGIN
    select * from  ARTICLE_MANAGE order by article_id desc
END

如何在存在条件下执行子查询？

How to execute sub query in if exists condition?

sql

subquery