# SQL execution order

Execution order for SQL clauses in QuestDB. This covers the SQL keywords you may already be familiar with as well as extensions to the language that are unique to QuestDB.

QuestDB attempts to implement standard ANSI SQL. We also try to be compatible
with PostgreSQL, although parts of this are a work in progress. QuestDB
implements these clauses which have the following execution order:

1. [FROM](/docs/query/sql/select/)
2. [ON](/docs/query/sql/join/)
3. [JOIN](/docs/query/sql/join/)
4. [WHERE](/docs/query/sql/where/)
5. [LATEST ON](/docs/query/sql/latest-on/)
6. [GROUP BY](/docs/query/sql/group-by/) (optional)
7. [WITH](/docs/query/sql/with/)
8. [HAVING](/docs/concepts/deep-dive/sql-extensions/#implicit-having) (implicit)
9. [SELECT](/docs/query/sql/select/)
10. [DISTINCT](/docs/query/sql/distinct/)
11. [ORDER BY](/docs/query/sql/order-by/)
12. [LIMIT](/docs/query/sql/limit/)

We have also implemented sub-queries that users may execute at any part of a
query that mentions a table name. The sub-query implementation adds almost zero
execution cost to SQL. We encourage the use of sub-queries as they add flavors
of functional language features to traditional SQL.

For more information on the SQL extensions in QuestDB which deviate from ANSI
SQL and PostgreSQL, see the
[SQL extensions documentation](/docs/concepts/deep-dive/sql-extensions/).