sql - 为什么 EXEC 会报告必须声明标量变量的错误

Question

我一直在为下面的脚本而苦苦挣扎，我想不出更好的方法来做到这一点。
有没有人看到问题？我正确地声明了变量。为什么会失败？谢谢你的帮助！

DECLARE @var1 as VarChar(50) 
DECLARE @var2 as VarChar(50) 

SET @Var1 = '1, 2, 3, 4, 5'

EXEC('IF (select count(*) from Table1 where Column1 in (' + @Var1 + ')) = 5 
     SET @Var2 = ''True''
ELSE 
     SET @Var2 = ''False''')

SELECT @Var2

错误信息：

必须声明标量变量@Var2

Answer 1

sp_executesql如果要从参数中获取值，则需要使用。

要缩短查询，请使用CASE.

DECLARE @var1 as VarChar(50) 
DECLARE @var2 as VarChar(50) 
SET @Var1 = '1, 2, 3, 4, 5'
SET @sqlCommand = 'SELECT @Var = CASE WHEN count(*) = 5 THEN ''TRUE'' ELSE ''FALSE'' END FROM Table1 where Column1 IN (' + @Var1 + ')'
EXECUTE sp_executesql @sqlCommand, N'@Var VARCHAR(5) OUTPUT', @Var=@var2 OUTPUT
SELECT @Var2

如果您想知道所有IDfrom@Var1是否存在于桌子上，您还需要使用DISTINCT

SET @sqlCommand = 'SELECT @Var = CASE WHEN count(DISTINCT Column1) = 5 THEN ''TRUE'' ELSE ''FALSE'' END FROM Table1 where Column1 IN (' + @Var1 + ')'

• sp_executesql ^{MSDN 文档}

Answer 2

由于 exec 正在执行单引号内的 SQL 的动态部分。但是@var2 在 exec 之外声明。要解决此问题，请在 exec 中声明并选择 @var2 或使用 @var2 作为 set '+@var2+'

Answer 3

使用 sp_executeSQL 而不是 exec 并使用输出参数

例如，如何将 sp_executesql 结果转换为变量？

例如

DECLARE @var1 as VarChar(50) 
DECLARE @var2 as VarChar(50) 
DECLARE @ParmDefinition nvarchar(500);
SET @Var1 = '1, 2, 3, 4, 5'

SET @ParmDefinition = N'@Var2  VarChar(50) OUTPUT';

DECLARE @sSQL nvarchar(500);

set @sSQL =  'IF (select count(*) from Table1 where Column1 in (' + @Var1 + ')) = 5 
     SET @Var2 = ''True''
ELSE 
     SET @Var2 = ''False'''

EXEC sp_executesql @sSQL, @ParmDefinition, @Var2=@Var2 OUTPUT;

SELECT @Var2;

Answer 4

那里有两件事..首先“;”在哪里 结束句子。您还需要对 varchar 值进行转义。

同意其他答案...使用 sp_executeSQL 运行动态 sql。

一个声明的例子......

USE AdventureWorks2012;
GO
DECLARE @find varchar(30); 
/* Also allowed: 
DECLARE @find varchar(30) = 'Man%'; 
*/
SET @find = 'Man%'; 
SELECT p.LastName, p.FirstName, ph.PhoneNumber
FROM Person.Person AS p 
JOIN Person.PersonPhone AS ph ON p.BusinessEntityID = ph.BusinessEntityID
WHERE LastName LIKE @find; 

sp_executeSQL 的示例..

DECLARE @IntVariable int;
DECLARE @SQLString nvarchar(500);
DECLARE @ParmDefinition nvarchar(500);

/* Build the SQL string one time.*/
SET @SQLString =
     N'SELECT EmployeeID, NationalIDNumber, Title, ManagerID
       FROM AdventureWorks.HumanResources.Employee 
       WHERE ManagerID = @ManagerID';
SET @ParmDefinition = N'@ManagerID tinyint';
/* Execute the string with the first parameter value. */
SET @IntVariable = 197;
EXECUTE sp_executesql @SQLString, @ParmDefinition,
                      @ManagerID = @IntVariable;
/* Execute the same string with the second parameter value. */
SET @IntVariable = 109;
EXECUTE sp_executesql @SQLString, @ParmDefinition,
                      @ManagerID = @IntVariable;

Answer 5

远离执行 sql 字符串的原因有很多。我会将其重写为：

declare @cnt int

select @cnt = count(1) 
from Table1 
where Column1 in
    (select items
    from dbo.Split(@Var1,',')
    )

return @cnt   -- then the calling function says if this is true or false.

对于拆分功能，请参见： 这里