In which sequence are queries and sub-queries executed by the SQL engine?

Question

Hello I made a SQL test and dubious/curious about one question:

In which sequence are queries and sub-queries executed by the SQL engine?

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Answer 1

The SQL engine tries to optimise the order in which (sub)queries are executed. The part deciding about that is called a query optimizer. The query optimizer knows how many rows are in each table, which tables have indexes and on what fields. It uses that information to decide what part to execute first.