Regular Session

Anatomy of a Join [DBA-302]

Speaker: Luke Jian

Duration: 75 minutes

Track: Enterprise Database Administration & Deployment

A good understanding of join algorithms is essential in diagnosing and fixing issues related to bad query plans. However, one of today’s realities is that a lot of database professionals do not have a computer science degree and didn’t sit through a formal “Introduction to Relational Databases” course. This session seeks to fill in some of the gaps that might exist by looking in-depth at the three types of join operations.

We’ll visualize how the join operations’ algorithms work so you can understand how query plans are computed, and then we’ll look at why these join operations have very different performance characteristics and why the optimizer chooses a specific join operator to use in a query plan. You’ll see through demonstrations that empirical cost calculations are similar to what the query optimizer actually returns. 


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