<programlisting>

SELECT *

FROM weather LEFT OUTER JOIN cities ON (weather.city = cities.name);

</programlisting>

<screen>

city | temp_lo | temp_hi | prcp | date | name | location

---------------+---------+---------+------+------------+---------------+-----------

Hayward | 37 | 54 | | 1994-11-29 | |

San Francisco | 46 | 50 | 0.25 | 1994-11-27 | San Francisco | (-194,53)

San Francisco | 43 | 57 | 0 | 1994-11-29 | San Francisco | (-194,53)

(3 rows)

</programlisting>

</screen>

This query is called a <firstterm>left outer

join</firstterm> because the table mentioned on the left of the

FROM weather W1, weather W2

WHERE W1.temp_lo &lt; W2.temp_lo

AND W1.temp_hi &gt; W2.temp_hi;

</programlisting>

<screen>

city | low | high | city | low | high

---------------+-----+------+---------------+-----+------

San Francisco | 43 | 57 | San Francisco | 46 | 50

Hayward | 37 | 54 | San Francisco | 46 | 50

(2 rows)

</programlisting>

</screen>

Here we have relabeled the weather table as <literal>W1</literal> and

<literal>W2</literal> to be able to distinguish the left and right side