QuestDB attempts to implement standard ANSI SQL. We also attempt to be PostgreSQL compatible, although some of it is work in progress. QuestDB implements the following clauses in this execution order:
- LATEST BY
- GROUP BY (implicit)
- HAVING (implicit)
- ORDER BY
We also implemented sub-queries. They can be used anywhere table name is used. Our sub-query implementation adds virtually zero execution cost to SQL. We encourage their use to add flavours of functional language to old-school SQL.