Because several database platforms are case-insensitive and tend to convert table and field names to either uppercase (e.g. Oracle) or lowercase (e.g. PostgreSQL), we use snake_case. All names should be in lowercase.

Good

SELECT COUNT(*) AS person_count FROM person

Bad

SELECT COUNT(*) AS personCount FROM person

SELECT COUNT(*) AS Person_Count FROM person

SELECT COUNT(*) AS PERSON_COUNT FROM person