Tips, Tricks, and Advice from the SQL Server Query Processing Team

Hash Warning SQL Profiler Event

One of the less well-known warning events that is logged to SQL Profiler trace is the Hash Warning event . Hash Warning events are fired when a hash recursion or hash bailout has occurred during a hashing operation. Both of these situations are less than

What's this cost?

Oftentimes when people include actual execution plan (Ctrl-M, see previous posts for a good primer on execution plans) while executing a batch in SQL Server Management Studio, and they see this "Query cost (relative to the batch)" thing on top of each query in the batch, they start to ask: What does this mean? But when I run this batch, the first query runs a faster than the second, and yet this crazy SQL Server says the second has a higher cost, what are they talking about?