Question

Can someone help please I dont know what I am doing wrong:

IF EXISTS ( SELECT  name
        FROM    sys.tables
        WHERE   name = N'MemberIdsToDelete' ) 
DROP TABLE [MemberIdsToDelete];
GO

SELECT  mm.memberid ,
        mm.aspnetuserid ,
        mm.email ,
        mm.RowNum AS RowNum
INTO    #MemberIdsToDelete
FROM    membership.members AS mm
        LEFT JOIN aspnet_membership AS asp ON mm.aspnetuserid = asp.userid
        LEFT JOIN trade.tradesmen AS tr ON tr.memberid = mm.memberid
WHERE   asp.isapproved = 0
        AND tr.ImportDPN IS NOT NULL
    AND tr.importDPN <> ''
ORDER BY mm.memberid

DECLARE @MaxRownum INT
SET @MaxRownum = ( SELECT   MAX(RowNum)
                   FROM     #MemberIdsToDelete
                 )

DECLARE @Iter INT
SET @Iter = ( SELECT    MIN(RowNum)
              FROM      #MemberIdsToDelete
            )

DECLARE @MemberId INT
DECLARE @TrademId INT
DECLARE @UId UNIQUEIDENTIFIER
DECLARE @Successful INT
DECLARE @OutputMessage VARCHAR(200)
DECLARE @Email VARCHAR(100)
DECLARE @Username VARCHAR(100)

SELECT  @MemberId = memberId ,
        @UId = AspNetUserId
FROM    MemberIdsToDelete
SELECT  @TrademId = TradesManId
FROM    trade.TradesMen
WHERE   memberId = @MemberId;

WHILE @Iter <= @MaxRownum 
  BEGIN
    SELECT  *
    FROM    #MemberIdsToDelete
    WHERE   RowNum = @Iter
  --more code here
    SET @Iter = @Iter + 1
  END

I just want to check if my table MemberIdsToDelete exists, if so drop it,
create MemberIdsToDelete with the results set from the select
loop through MemberIdsToDelete table and perform operations

I am getting error that RowNum does not exist

Answer 1

For a start, to check if a table exists and then drop accordingly, you need to use something like

IF EXISTS (SELECT name 
           FROM sys.tables 
           WHERE name = N'MemberIdsToDelete') 
DROP TABLE [MemberIdsToDelete];
GO

as for the error, your RowNum column does not exist when you are attempting to reference it. Include it in the SELECT statement

select mm.memberid, mm.aspnetuserid, mm.email, mm.RowNum AS RowNum    
into #MemberIdsToDelete     
from membership.members as mm      
    left join aspnet_membership as asp       
        on mm.aspnetuserid=asp.userid       
            left join trade.tradesmen as tr       
                on tr.memberid=mm.memberid       
where asp.isapproved = 0 and tr.ImportDPN IS NOT NULL 
    and tr.importDPN <> '' 
order by mm.memberid;
GO  

I hope this helps.

Edit. Based on you additional error from your comment. You are now attempting to access a temporary table that does not exist. You must first populate the temporary table #MemberIdsToDelete before attempting to read from it. The invalid column error is down to the same problem. You are attempting to read a column called RowNum from the temporary table which does not exist.

Edit2. Remove the ‘#’ from the #MemberIdsToDelete. You are inserting into a table not a temporary table. Or, Add a # to the select into above (see the code above). This will make it a temporary table as required.