Databases · Junior · Question 29 of 75

Why does `SELECT city, name, COUNT(*) FROM users GROUP BY city` fail?

1You can't group by text columns
✓Correct answer: name is neither grouped nor aggregated, so there is no single value per city
3COUNT(*) can't be used with GROUP BY

Explanation

Each output row is a group. Every selected column must be in GROUP BY or wrapped in an aggregate like MAX(name) or string_agg(name, ', ').

Further reading

PostgreSQL: Aggregate functions ↗

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