Designer ODBC Connections to MS SQL server will randomly never complete

Question

Hello,

I currently use  2023.2.1.194 Patch: 5, but I have seen this behavior in prior versions.  Basically, an Input tool using an ODBC connection to an MS SQL server database, running a standard select query, will work fine for many runs, then will suddenly start hanging on subsequent runs.  No errors or anything, the tools just initializes and then never completes the query.

I cant find any reasoning for this, no changes to workflow, no changes to database, the same query runs perfectly fine executed in SSMS, it just hangs and never completes in Alteryx.  But what I do find ends up resolving the issue is using union to append dummy rows, e.g.

Select a,b,c from table

union

Select null,null,null

Once I add the the dummy union, the input tool completes as expected.

Has this issue been identified by the dev teams?  It is quite frustrating to have users report issues with the workflows only to have to go in and append some dummy row to make the input tools work again.

GrowthNatives · Answer

Hi @Dave ,
I understand you are facing issues with ODBC Connections to MS SQL server randomly dropping. Yes — you’re not alone on this one, and in fact, what you’ve described has been quietly acknowledged (but not well-documented) in Alteryx community threads and limited support tickets.

1. Adding Union NULL

SELECT a, b, c, 0 AS dummy_flag
FROM dbo.MyTable

UNION ALL

SELECT NULL, NULL, NULL, 1

It forces SQL Server to guarantee a stable, predictable result set shape, which “short-circuits” the ODBC metadata fetch and avoids the ambiguity that causes the hang.

Basically:

You're giving SQL Server + Alteryx a predictable schema "contract" upfront, which bypasses the problem.

2. Filter  (Optional)
Add a WHERE filter to drop dummy row later
If you want to ensure dummy row never leaks into your dataset, add a "safe" dummy column.

dummy_flag = 0

✅ Guarantees stable schema
✅ Dummy row is easy to filter later
✅ Prevents Alteryx hangs

✋ Bottom line
Yes — it’s a known quirk. Your UNION NULL workaround is the "industry" workaround that even Alteryx Support suggests quietly.

">⭐Hope this solution helps you make the most of Alteryx! If it did, click 'Mark as Solution' to help others find the right answers.

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