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Diffstat (limited to 'doc/src/FAQ.html')
| -rw-r--r-- | doc/src/FAQ.html | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/doc/src/FAQ.html b/doc/src/FAQ.html index a71b00f90e3..e549bb98a45 100644 --- a/doc/src/FAQ.html +++ b/doc/src/FAQ.html @@ -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> |