From the course: Advanced SQL – Window Functions
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Logical query processing review - SQL Tutorial
From the course: Advanced SQL – Window Functions
Logical query processing review
- [Instructor] For those of you who haven't yet watched my query processing course, this video is going to be a speed-of-light review of some of the main concepts. Every query begins with the FROM clause, where the data set for the query is constructed. The data sources may be anything from a single table and up to joins of 50 shades of various different sources. All data sources, join qualifications, and reservations are evaluated and placed into a single data set that is then passed to the WHERE clause. WHERE evaluates each row using logical predicates. Rows for which the predicate evaluates to true will live to see another clause. All others are discarded, never to be seen again by the query. Then, this filtered set is passed to the GROUP BY clause. GROUP BY changes the fundamental structure of the set, from individual rows into row groups based on the grouping expressions. The group set is then shipped to the HAVING…
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