This second chapter of the part on Azure SQL performance and optimization focuses on the actual queries executed by the SQL engine sent from the external workload. Knowing what queries consume the most resources and take the most time to execute allows us to focus improvement efforts on queries that have significant impact on the overall system performance. Most SQL systems exhibit performance skew with a few queries consuming the most resources. This pattern stays consistent, but the exact “top consumer” queries can change over time as data sizes grow and users use the system in new and different ways. This skew helps us with performance management. We can focus on a small number of queries that will maximize our impact rather than having to make improvements to many queries with little impact for each.