Question

I have a database with dynamically generated tables. I’m writting a stored procedure to execute queries over the generated tables and I need to see the results in the query analyzer tool (or alike).

What I currently have is:

DECLARE @TableName sysname

DECLARE TableNameCursor CURSOR FOR
SELECT TableName FROM [xxxTables] WHERE xxx...

OPEN TableNameCursor
FETCH NEXT FROM TableNameCursor INTO @TableName

WHILE @@FETCH_STATUS = 0
BEGIN
    DECLARE @Query nvarchar
    SET @Query = 'SELECT * FROM ' + @TableName
    EXEC sp_executesql @Query

    -- This is executed as long as the previous fetch succeeds.
    FETCH NEXT FROM TableNameCursor INTO @TableName
END

But as I have multiple selects I’m not getting the output. How can I fix the stored procedure to show the result?

All the tables have the same layout so I can join them.

Answer 1

Unless this is merely a typo produced when posting the script here, I might have finally found the issue. You haven’t specified the maximum length for the @Query variable:

DECLARE @Query nvarchar

In this context the maximum length defaults to 1, as per the manual:

When n is not specified in a data definition or variable declaration statement, the default length is 1. When n is not specified with the CAST function, the default length is 30.

When you are assigning a query string to @Query, it only stores the first character. Naturally, when you are later trying to execute the query, it returns nothing and should produce an error instead.

You can fix it by specifying a maximum length. In SQL Server 2005 or later version, it could be an explicit number (up to 4000) or max:

DECLARE @Query nvarchar(max)

In earlier versions max is not supported, so just use an explicit number:

DECLARE @Query nvarchar(4000)