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SQL Server FAQ - Using Subqueries with the EXISTS Operators

By: FYIcenter.com

(Continued from previous topic...)

How To Use Subqueries with the EXISTS Operators?

A subquery can be used with the EXISTS operator as "EXISTS (subquery)", which returns true if the subquery returns one or more rows. The following statement is a good example of "EXISTS (subquery)". It returns rows from fyi_links table that there are rows existing in the fyi_rates table with the same id.

SELECT id, url, tag, YEAR(created) As year 
   FROM fyi_links WHERE EXISTS (
   SELECT * FROM fyi_rates 
   WHERE fyi_rates.id = fyi_links.id)
id      url                     tag     Year
101     dev.fyicenter.com       DEV     2006
102     dba.fyicenter.com       DBA     2007
103     sqa.fyicenter.com       SQA     2007

Note that the subquery uses columns from the source table of the outer query.

(Continued on next topic...)

  1. How To Join Two Tables in a Single Query?
  2. How To Write a Query with an Inner Join?
  3. How To Define and Use Table Alias Names?
  4. How To Write a Query with a Left Outer Join?
  5. How To Write a Query with a Right Outer Join?
  6. How To Write a Query with a Full Outer Join?
  7. How To Write an Inner Join with the WHERE Clause?
  8. How To Name Query Output Columns?
  9. What Is a Subquery in a SELECT Query Statement?
  10. How To Use Subqueries with the IN Operators?
  11. How To Use Subqueries with the EXISTS Operators?
  12. How To Use Subqueries in the FROM Clause?
  13. How To Count Groups Returned with the GROUP BY Clause?
  14. How To Return the Top 5 Rows from a SELECT Query?
  15. How To Return the Second 5 Rows?
  16. How To Use UNION to Merge Outputs from Two Queries Together?
  17. How To Use ORDER BY with UNION Operators

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