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SQL Server FAQ - "LEFT OUTER JOIN ... ON" - Writing Queries with Left Outer Joins

By: FYIcenter.com

(Continued from previous topic...)

How To Write a Query with a Left Outer Join?

If you want to query from two tables with a left outer join, you can use the LEFT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a left outer join from two tables: fyi_links and fyi_rates. The join condition is that the id in the fyi_links table equals to the id in the fyi_rates table:

SELECT l.id, l.url, r.comment FROM fyi_links l 
   LEFT OUTER JOIN fyi_rates r ON l.id = r.id
id      url                     comment
101     dev.fyicenter.com       The best
102     dba.fyicenter.com       Well done
103     sqa.fyicenter.com       Thumbs up
104     www.mysql.com           NULL
105     www.oracle.com          NULL
106     www.php.net             NULL
107     www.winrunner.com       NULL

Note that a left outer join may return extra rows from the first (left) table that do not satisfy the join condition. In those extra rows, columns from the second (right) table will be given null values.

The extra rows returned from the left outer join in this example represents links that have no rates in the above example.

(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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