January 2019
Beginner
556 pages
14h 19m
English
Content preview from Learning PostgreSQL 11 - Third Edition
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Window functions
Apart from grouping and aggregation, PostgreSQL provides another way to perform computations based on the values of several records. It can be done using window functions. Grouping and aggregation mean one single output record for every group of several input records. Window functions can do similar things, but they are executed for every record, and the number of records in the output and the input is the same:
GROUP BY and window functions
In the preceding diagram, the rectangles represent the records of a table. Let's assume that the color of the rectangles indicates the value of a field used to group the records. When ...
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