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Aggregation Functions

Aggregation functions perform some operations on a set of rows. These include

  • Avg
  • Min
  • Max
  • Sum
  • Count

Example

SELECT count(*) FROM my_table

GROUP BY

GROUP BY keyword groups entries by some equality on some attribute * note that whichever attribute you choose to group by must be present in the SELECT clause

HAVING

HAVING keyword is the same as where, except it acts after group by

Example

SELECT dept_name, avg(salary) as avg_salary
FROM instructor
GROUP BY dept_name
HAVING avg(salary) > 42000;