Select Non Grouped Column - Developer Roadmap

If you SELECT a column not in the GROUP BY clause, it will throw an error stating that the column must be in the GROUP BY clause or in an aggregate function. Let's use the table below as an illustration.

firstName	lastName	phoneNumber
John	Doe	+23410910
Jack	Ray	+23410911
Irene	Rotherdam	+23410911

If you run the query below against the database:

sql

SELECT firstName, phoneNumber FROM phoneNumbers
GROUP BY phoneNumber

The result will be an error because firstName is not in the GROUP BY clause and not using an aggregate function.