Question

i have a database table with a list of sql views

i want to create a new view or stored procedure that based on which views are in that table will return those views unioned
like this

SELECT     ALINE1, HOME, EMAIL, EXPIRE, EDATE7, type
    FROM         dbo.campaign_membership_30
    UNION ALL
    SELECT     ALINE1, HOME, EMAIL, EXPIRE, EDATE7, type
    FROM         dbo.campaign_membership_30n
    UNION ALL
    SELECT     ALINE1, HOME, EMAIL, EXPIRE, EDATE7, type
    FROM         dbo.campaign_membership_60n
    UNION ALL
    SELECT     ALINE1, HOME, EMAIL, EXPIRE, EDATE7, type
    FROM         dbo.campaign_membership_today
    UNION ALL
    SELECT     ALINE1, BOOKNO, EMAIL, DEPART, DEP7, type
    FROM         dbo.depart_151days
    UNION ALL
    SELECT     ALINE1, BOOKNO, EMAIL, DEPART, DEP7, type
    FROM         dbo.depart_90Days

Answer 1

There are a lot of major caveats here.

First, using dynamic SQL is often dangerous. It can open up your database to SQL injection attacks. If you don’t understand what these are then you need to do a lot of educating of yourself before I would suggest that you use dynamic SQL.

Second, this kind of a pattern (storing tables and columns in a table from which to generate SQL) is a really bad pattern. There are many problems with it. I can’t suggest alternative solutions though without knowing more about your application/problem space.

That said, the following is a simplistic version of how it might work in SQL Server 2005. This does not include error handling, etc.

DECLARE @sql VARCHAR(MAX)  -- NVARCHAR if you use unicode characters in table names

SELECT
    @sql = dbo.Concatenated_Rows('SELECT col1, col2 FROM ' + MT.table_name + ' UNION ALL ')
FROM
    dbo.My_Table MT

-- Remove the extra UNION ALL
SELECT @sql = SUBSTRING(@sql, 1, LEN(@sql) - 11)

EXEC(@sql)

The function Concatenated_Rows would have to be written. You could alternatively use a cursor or maybe even FOR XML to create the concatenated string. Here’s a link that does a good job explaining many of the possible methods and does a good job of comparing them.

Again, there are probably better solutions out there then going this route, especially if this is more than a one-off task.