In SQL, the order of execution for a query is as follows:
- FROM clause: The first step in executing a SQL query is to identify the tables from which the data will be retrieved. This is done in the FROM clause.
- WHERE clause: The WHERE clause is used to filter the data based on specific conditions. It is executed after the FROM clause, and before any grouping or sorting is performed.
- GROUP BY clause: If the query includes a GROUP BY clause, the data is grouped together based on the specified columns. This step is executed after the WHERE clause.
- HAVING clause: The HAVING clause is used to filter the grouped data based on specific conditions. It is executed after the GROUP BY clause.
- SELECT clause: The SELECT clause is used to specify the columns to be retrieved from the tables. It is executed after the WHERE, GROUP BY, and HAVING clauses.
- ORDER BY clause: If the query includes an ORDER BY clause, the data is sorted based on the specified columns. This step is executed after the SELECT clause.