From the course: Database Foundations: Database Management
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Reading execution plans
From the course: Database Foundations: Database Management
Reading execution plans
- [Instructor] When processing queries, the database servers query optimizer determines how to perform the task at hand. Which exact steps to take, in which sequence are needed to best arrive at the final solution. The path that's chosen is known as the queries execution plan. And these plans are available to look at anytime that you want. Reviewing execution plans can give you critical insight into what the database query processor is actually doing behind the scenes. This information can guide optimization efforts and help you write more performant queries. The important thing to know about an execution plan, is that it's developed before any actual data is read from your data tables. So the optimizer knows basic information about the structure of the table and whether any particular columns have indexes. It will also sometimes know and approximate number of data rows that the table contains and some additional statistics about the distribution of values. But it doesn't know…
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