The main query never executes before the sub-query, which is always executed first. First, subqueries are resolved. The outer query's input comes from the subquery's output.
What is the order of execution in SQL?
The inner query is referred to as a subquery, and the outer query is known as the main query. Every time, a subquery is run, the results are then passed on to the main query. Similar to how mathematical operations follow the PEMDAS or BIDMAS rules, SQL queries follow a particular order when evaluating clauses. The clauses in queries are executed in the following order:
1. FROM/JOIN is first used to identify the relevant data.
2. WHERE: used to eliminate records that don't fit the criteria.
3. GROUP BY: used to divide the data into groups according to the contents of one or more columns.
4. HAVING: the created grouped records that don't adhere to the constraints removed.
5. SELECT is used to create the desired number of columns and expressions.
6. The ORDER BY command is used to order the derived values either ascending or descending.
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