What are statistics and why should the developer care?

Imagine you're a developer in a small shop, and you experience some degradation of performance in your business-critical ERP system, literally over the weekend. So you are tasked with bringing back that performance, because somehow you also inherited the "accidental DBA " role. Hardware is OK, the network is OK, and your application hasn't changed lately, either. Now what? Let me take you for a quick dive into how your queries get analyzed and optimized by the SQL Server engine. You'll learn about statistics (also about density and cardinality), why they are important, ways to explore them and the techniques to keep them up to date, in order to achieve optimal query plans.