SQL Server: Deadlocks occurring during simultaneous updates on a large table with multiple indexes
I'm stuck on something that should probably be simple... This might be a silly question, but I'm working with an scenario with deadlocks when multiple transactions attempt to update rows in a large table with several indexes in SQL Server 2019. The table contains around 1 million records and is indexed on multiple fields, which I thought would help with performance, but it seems to be causing deadlock situations instead. I've tried isolating the transactions by using the `ROWLOCK` hint, but the deadlocks still occur. Here's a simplified version of the update query I am using: ```sql BEGIN TRANSACTION; UPDATE MyLargeTable SET ColumnA = 'NewValue' WHERE ColumnB = 'SomeValue'; COMMIT TRANSACTION; ``` I have noticed that when two transactions run concurrently, one trying to update `ColumnA` and the other trying to update `ColumnC`, they often end up waiting on each other. The behavior I receive is: ``` Transaction (Process ID XX) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction. ``` I have enabled deadlock tracing using the following command: ```sql DBCC TRACEON (1222, -1); ``` From the deadlock graph output, it seems that the contention is mostly on indexes. I'm considering reorganizing the indexes or possibly using a different isolation level like `READ COMMITTED SNAPSHOT`, but I'm unsure if that would help or just delay the scenario. Has anyone encountered a similar situation, and what strategies did you implement to resolve deadlocks in SQL Server for large tables with multiple updates happening concurrently? This is part of a larger application I'm building. Thanks in advance! I'm working on a service that needs to handle this. Is there a better approach?