How To Use Subqueries in the FROM clause

Q

How To Use Subqueries in the FROM clause? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements

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A

If you have a query returning many rows of data, and you want to perform another query on those rows, you can put the first query as a subquery in the FROM clause of the second query. The following statement shows you how to use a subquery as base table for the main query:

SQL> SELECT * FROM (
  2    SELECT first_name, last_name, department_name
  3    FROM employees e, departments d 
  4    WHERE e.department_id = d.department_id
  5  ) WHERE department_name LIKE 'S%' ORDER BY last_name;
FIRST_NAME        LAST_NAME              DEPARTMENT_NAME
----------------- ---------------------- ---------------
Ellen             Abel                   Sales
Sundar            Ande                   Sales
Mozhe             Atkinson               Shipping
Amit              Banda                  Sales
Elizabeth         Bates                  Sales
Sarah             Bell                   Shipping
......

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