SELECT
clause of a query, and they perform computations over sets of values in multiple rows of our relations. The basic aggregation functions supported by every SQL systems are: MIN
, MAX
, SUM
, AVG
, and COUNT
.GROUP BY
, and the HAVING
clauses.GROUP BY
allows us to partition our relations into groups, and then compute aggregated aggregate functions over each group independently.HAVING
condition allows us to test filters on the results of aggregate values.WHERE
and HAVING
conditions is the HAVING
applies to all the groups generated from the GROUP BY
clause. While the WHERE
condition applies to single rows at a time.