MS SQL Server Interview Question:

How To Write a Query with a Left Outer Join in MS SQL Server?

Submitted by: Administrator

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: ggl_links and ggl_rates. The join condition is that the id in the ggl_links table equals to the id in the ggl_rates table:

SELECT l.id, l.url, r.comment FROM ggl_links l
LEFT OUTER JOIN ggl_rates r ON l.id = r.id
GO
id url comment
101 www.globalguideline.com The best
102 www.globalguideline.com/html Well done
103 www.globalguideline.com/sql Thumbs up
104 www.google.com NULL
105 www.yahoo.com NULL
106 www.php.net NULL
107 www.mysql.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.
Submitted by: Administrator