sql-aggregates

Question 1

What are some examples of aggregate functions?

Answer 1

max(), sum(), min(), every(), count(), json.agg()

Question 2

What is the purpose of a group by clause?

Answer 2

To separate rows into groups and perform aggregate functions on those groups of rows. Partitions the results by the part you don’t want duplicates of.

Question 3

What is the rule for select and group by for aggregate functions

Answer 3

Columns from select that are not aggregate functions need to appear in group by unless you can replace that column by a unique id.