SQL Server: issue with declaring variable in dynamic SQL

Question

I created a dynamic stored procedure that starts as follows.

I can save this without errors but when I execute it it seems it doesn't recognise the @temp variable as it throws the following error: "Must declare the table variable "@temp"."

Could this be because of wrong quotes / escaping and if, how do I have to change this in order to have it right (I am pretty new to SQL so some of the quotes could be wrong or missing) ?

My SP (first part):

    @selection nvarchar(100)
AS
BEGIN

    SET NOCOUNT ON;

    BEGIN

    DECLARE @temp AS TABLE
    (
        ranking int,
        item nvarchar(100),
        groupCount int,
        groupName nvarchar(100)
    )

    DECLARE @sql nvarchar(max)

    SET @sql = '
    INSERT INTO @temp
    (       
                ranking,
                item,
                groupCount,
                groupName
    )
    SELECT      RANK() OVER(ORDER BY COUNT(*) desc, policy) [Rank],
                ' + @selection + ', 
                COUNT(*) AS groupCount,
                ''currentMonth'' AS groupName
    FROM        Log_PE 
    WHERE       CONVERT(DATE, dateEsc, 120) >= CONVERT(DATE, CONVERT(VARCHAR(6), GETDATE(), 112) + ''01'', 112)
    GROUP BY    ' + @selection + '
    ORDER BY    groupCount desc, ' + @selection + '
        ...

Many thanks in advance for any help with this, Mike.

Answer 1

As I have already mentioned in comments section, Dynamic Sql has its own scope, any variable declared outside of that scope arent visible to dynamic sql, Your have to declare the variable inside your dynamic sql. Something like as follows....

SET @sql = N' DECLARE @temp AS TABLE
             (
              ranking int,
              item nvarchar(100),
              groupCount int,
              groupName nvarchar(100)
              )

INSERT INTO @temp
(       
            ranking,
            item,
            groupCount,
            groupName
)
SELECT      RANK() OVER(ORDER BY COUNT(*) desc, policy) [Rank],
            ' + @selection + ', 
            COUNT(*) AS groupCount,
            ''currentMonth'' AS groupName
FROM        Log_PE 
WHERE       CONVERT(DATE, dateEsc, 120) >= CONVERT(DATE, CONVERT(VARCHAR(6), GETDATE(), 112) + ''01'', 112)
GROUP BY    ' + @selection + '
ORDER BY    groupCount desc, ' + @selection + '

Answer 2

Hope you are doing fine, well i think you may reconsider using a variable table because SQL won't understand what the @temp variable means when you will execute the EXEC(@sql), i recommand using a temp table instead of a variable table, here's the new code :

BEGIN

    SET NOCOUNT ON;

    BEGIN

if object_id('temp') is not null
  drop table temp

create table temp
    (
        ranking int,
        item nvarchar(100),
        groupCount int,
        groupName nvarchar(100)
    )

    DECLARE @sql nvarchar(max)

    SET @sql = '
    INSERT INTO temp
    (       
                ranking,
                item,
                groupCount,
                groupName
    )
    SELECT      RANK() OVER(ORDER BY COUNT(*) desc, policy) [Rank],
                ' + @selection + ', 
                COUNT(*) AS groupCount,
                ''currentMonth'' AS groupName
    FROM        Log_PE 
    WHERE       CONVERT(DATE, dateEsc, 120) >= CONVERT(DATE, CONVERT(VARCHAR(6),     GETDATE(), 112) + ''01'', 112)
    GROUP BY    ' + @selection + '
    ORDER BY    groupCount desc, ' + @selection + '

...

if object_id('temp') is not null
  drop table temp

I hope thiw will help you

Answer 3

When you EXEC or sp_executesql, you get another name space (scope) for the process space. Change from a table variable to a local temp table, #temp.

Below is a quick example using sp_who2 illustrating use of a local temp table.

Sincerely

J

Code Snippet

-- CREATE LOCAL TABLE
CREATE TABLE #WHO2
(
  [spid] int not null
, [status] varchar (255) not null
, [login] varchar (255) not null
, [host_name] varchar (255) not null
, [blk_by] varchar(10) not null
, [db_name] varchar (255) null
, [command] varchar (255) not null
, [cpu_time] int not null
, [disk_io] int not null
, [last_batch] varchar (255) not null
, [program_name] varchar (255) null
, [spid2] int not null
, [request_id] int not null
); ;

-- DYNAMIC SQL      
DECLARE @VAR_TSQL VARCHAR(MAX);      
SET @VAR_TSQL = 'INSERT #WHO2 EXEC sp_who2';
EXECUTE (@VAR_TSQL);
GO

-- TABLE PERSISTS UNTIL SPID (CONNECTION) IS BROKEN
SELECT * FROM #WHO2