|
|
|
@ -137,7 +137,9 @@ am running? <BR> |
|
|
|
|
large obj descriptor.</I> Why?<BR> |
|
|
|
|
<A HREF="#4.22">4.22</A>) How do I create a column that will default to the |
|
|
|
|
current time?<BR> |
|
|
|
|
<A HREF="#4.23">4.23</A>) Why are my subqueries using <CODE>IN</CODE> so slow?<BR> |
|
|
|
|
<A HREF="#4.23">4.23</A>) Why are my subqueries using <CODE>IN</CODE> so |
|
|
|
|
slow?<BR> |
|
|
|
|
<A HREF="#4.24">4.24</A>) How do I do an <i>outer</i> join?<BR> |
|
|
|
|
|
|
|
|
|
<H2><CENTER>Extending PostgreSQL</CENTER></H2> |
|
|
|
|
|
|
|
|
@ -1206,6 +1208,22 @@ to: |
|
|
|
|
</PRE></CODE> |
|
|
|
|
We hope to fix this limitation in a future release. |
|
|
|
|
|
|
|
|
|
<H4><A NAME="4.24">4.24</A>) How do I do an <i>outer</i> join?<BR></H4><P> |
|
|
|
|
PostgreSQL does not support outer joins in the current release. They can |
|
|
|
|
be simulated using <small>UNION</small> and <small>NOT IN</small>. For |
|
|
|
|
example, when joining <i>tab1</i> and <i>tab2,</i> the following query |
|
|
|
|
does an <i>outer</i> join of the two tables: |
|
|
|
|
<PRE> |
|
|
|
|
SELECT tab1.col1, tab2.col2 |
|
|
|
|
FROM tab1, tab2 |
|
|
|
|
WHERE tab1.col1 = tab2.col1 |
|
|
|
|
UNION ALL |
|
|
|
|
SELECT tab1.col1, NULL |
|
|
|
|
FROM tab1 |
|
|
|
|
WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2) |
|
|
|
|
ORDER BY tab1.col1 |
|
|
|
|
</PRE> |
|
|
|
|
|
|
|
|
|
<HR> |
|
|
|
|
|
|
|
|
|
<H2><CENTER>Extending PostgreSQL</CENTER></H2><P> |
|
|
|
|