SQL Server 2017: Difficulty handling unique constraint violation during upsert with MERGE statement
I need some guidance on I'm working on a project and hit a roadblock... I'm stuck on something that should probably be simple. I'm currently working with SQL Server 2017 and working with an scenario when performing an upsert operation using a `MERGE` statement. The scenario involves trying to insert or update records in a target table based on the incoming data from a staging table. However, I keep working with a unique constraint violation behavior when multiple records in the staging table match the same target record. Here’s the code I’m using: ```sql MERGE INTO TargetTable AS target USING StagingTable AS source ON target.KeyColumn = source.KeyColumn WHEN MATCHED THEN UPDATE SET target.ValueColumn = source.ValueColumn WHEN NOT MATCHED THEN INSERT (KeyColumn, ValueColumn) VALUES (source.KeyColumn, source.ValueColumn); ``` The unique constraint is on `KeyColumn`, and I’m wondering if there’s a way to handle this situation gracefully. I’ve tried adding a `WHERE` clause in the `WHEN MATCHED` section to filter the updates, but that didn't resolve the scenario. I'm also considering using a `TRY-CATCH` block to catch the behavior, but I'd prefer a more elegant solution that prevents the behavior from occurring in the first place. I have also explored using a temporary table to pre-aggregate the incoming data, but it adds unnecessary complexity. Is there a recommended approach to either modify my `MERGE` statement or restructure the logic to handle potential duplicates without violating the unique constraint? Any insights on best practices for this scenario would be greatly appreciated! For context: I'm using Sql on Ubuntu. What am I doing wrong? My development environment is Linux. What's the best practice here? I've been using Sql for about a year now. Any examples would be super helpful.