Duplicate post please see here

I would be more worried about why it has not passed in UAT and yet and yet has been released to production! Has something changed in the UAT environment since the code...

Could you please post DDL and include your sample data.

If it is a named instance use the port number too, do not forget to enable all ip addresses in SQL Configuration Management. Have you set up an SQL account...

Check out the string splitter function here

Ryanair had a similar issue earlier in the year (pilots and crew taking outstanding leave at the same time) with I think 18,000 cancellations, perhaps someone should look at  the similarities...

Good question to start the week thanks Steve.

The query also appears to include two databases and a collation conflict. Your DDL may need to include these too.

One method, if it is a workgroup and assuming it is the default instance, is to use SQL authentication; you will need to configure Windows Firewall to allow incoming connections (private ONLY)...

The advice you have had is all correct. Does the stored procedure point to the local server or remote server? Which one are you running it from? You seem to...