MySQL SQLLesson 36Free preview

MySQL GROUP BY

This lesson is part of MySQL · All levels

Summary

GROUP BY is used to group data rows based on one or more columns, e.g. per city, category, or department. Each group can then be calculated by an aggregate function such as COUNT, SUM, AVG, MAX, and MIN. Without GROUP BY, the aggregate function only produces one line for the entire data.

Key points

GROUP BY group rows based on the same column value
Aggregate functions such as COUNT, SUM, AVG, MAX, MIN are calculated per group
Columns selected in addition to the aggregate results must be in GROUP BY (mode ONLY_FULL_GROUP_BY)
It can group more than one column, for example GROUP BY city, role
The group's output can be filtered again by having

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