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Oracle Tutorials - Use Subqueries in the FROM Clause

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(Continued from previous topic...)

How To Use Subqueries in the FROM Clause?

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
......

(Continued on next topic...)

  1. What Is a SELECT Query Statement?
  2. How To Select All Columns of All Rows from a Table?
  3. How To Select Some Columns from a Table?
  4. How To Select Some Rows from a Table?
  5. How To Sort the Query Output?
  6. Can the Query Output Be Sorted by Multiple Columns?
  7. How To Sort Query Output in Descending Order?
  8. How To Use SELECT Statement to Count the Number of Rows?
  9. Can SELECT Statements Be Used on Views?
  10. How To Filter Out Duplications in Returning Rows?
  11. What Are Group Functions?
  12. How To Use Group Functions in the SELECT Clause?
  13. Can Group Functions Be Mixed with Non-group Selection Fields?
  14. How To Divide Query Output into Groups?
  15. How To Apply Filtering Criteria at Group Level?
  16. How To Count Duplicated Values in a Column?
  17. Can Multiple Columns Be Used in GROUP BY?
  18. Can Group Functions Be Used in the ORDER BY Clause?
  19. How To Join Two Tables in a Single Query?
  20. How To Write a Query with an Inner Join?
  21. How To Define and Use Table Alias Names?
  22. How To Write a Query with a Left Outer Join?
  23. How To Write a Query with a Right Outer Join?
  24. How To Write a Query with a Full Outer Join?
  25. How To Write an Inner Join with the WHERE Clause?
  26. How To Write a Left Outer Join with the WHERE Clause?
  27. How To Name Query Output Columns?
  28. What Is a Subquery?
  29. How To Use Subqueries with the IN Operator?
  30. How To Use Subqueries with the EXISTS Operator?
  31. How To Use Subqueries in the FROM Clause?
  32. How To Count Groups Returned with the GROUP BY Clause?
  33. How To Return Top 5 Rows?

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