Understanding the Problem: SQL Server Column-Value Issues

If you’ve ever worked with different versions of SQL Server, like 2000 and 2005, you may have noticed some inconsistencies, particularly regarding how function arguments are handled. A common stumbling block occurs when using columns as arguments to functions. Such issues not only interrupt workflow but can also be quite perplexing, especially when you encounter error messages that don’t clarify the problem.

In this post, we’ll investigate a particular case where SQL Server 2000 fails to process a query correctly while SQL Server 2005 executes it flawlessly.

The Scenario

Imagine you have a table called usertable containing a column legacyCSVVarcharCol that stores comma-separated lists of integers. When trying to create a view or execute a query that uses this column as an argument to a function, you might run into syntax errors that make it difficult to proceed.

Here’s the conflicting code:

-- Works in SQL Server 2005, fails in SQL Server 2000
CREATE VIEW foo AS    
SELECT usertable.legacyCSVVarcharCol AS testvar     
FROM usertable   
WHERE rsrcID IN
    (SELECT val     
     FROM dbo.fnSplitStringToInt(usertable.legacyCSVVarcharCol, ','))

You may encounter an error message like:

Msg 170, Level 15, State 1, Procedure foo, Line 4    
Line 25: Incorrect syntax near '.'.

Additionally, if you attempt to pass the alias of testvar to the function, it may lead to an even stranger error:

Msg 155, Level 15, State 1, Line 8
'testvar' is not a recognized OPTIMIZER LOCK HINTS option.

The Core Issue

So, what’s happening here? The root of the problem lies in the fact that SQL Server 2000 does not support passing column values as arguments to table-valued user-defined functions. In contrast, SQL Server 2005 introduced more flexibility and support for such operations.

Key Points to Consider:

• Column-Values in Functions: SQL Server 2000 restricts functions to accept only constants as arguments. This means any attempt to use a column or an alias will not work and result in errors.
• Legacy Code: If you’re maintaining legacy systems, it’s often the case that data is stored in an inefficient format, like CSV in a single column.

The Solution: Workarounds for SQL Server 2000

While there isn’t a straightforward fix to make SQL Server 2000 accept column values in functions, there are workarounds you can implement to achieve your goals.

Workaround Strategies

1. Use Hard-Coded Strings: If feasible, consider using hard-coded strings directly within your functions where it makes sense.

   SELECT t1.* 
   FROM usertable t1
   WHERE 1 IN 
       (SELECT val 
        FROM fnSplitStringToInt('1,4,543,56578', ','))
   

2. Temporary Tables or CTEs: You can pre-process data using a temporary table or a Common Table Expression (CTE) to convert your CSV lists into a usable format before passing them to functions.

   WITH ProcessedData AS (
       SELECT legacyCSVVarcharCol 
       FROM usertable
   )
   SELECT *
   FROM ProcessedData
   WHERE 1 IN (SELECT val FROM dbo.fnSplitStringToInt(ProcessedData.legacyCSVVarcharCol, ','))
   

3. Consider Upgrading: If maintaining compatibility with legacy systems is feasible, upgrading to SQL Server 2005 or later would be the most robust solution, as it offers enhanced function capabilities and eliminates many of these syntax issues.

Conclusion

Navigating differences between SQL Server versions can be challenging, but understanding the limitations of SQL Server 2000 concerning column values in functions can help you find alternative solutions. It’s crucial to keep these restrictions in mind when working with legacy databases.

While the best solution often is to adhere to proper database normalization practices, sometimes it may not be possible, especially with existing legacy codes. Hopefully, this guide helps you work through the issues and simplifies your SQL queries!