Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Sun Jun 23 17:16:13 EDT 2002
+ Last updated: Mon Jun 24 21:45:50 EDT 2002
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
using an index with ORDER BY and LIMIT:
SELECT col
FROM tab
- ORDER BY col
+ ORDER BY col [ DESC ]
LIMIT 1
When using wild-card operators such as LIKE or ~, indexes can only be
- used if the beginning of the search is anchored to the start of the
- string. Therefore, to use indexes, LIKE patterns must not start with
- %, and ~(regular expression) patterns must start with ^.
+ used if the default C local is used during initdb and the beginning of
+ the search is anchored to the start of the string. Therefore, to use
+ indexes, LIKE patterns must not start with %, and ~(regular
+ expression) patterns must start with ^.
4.9) How do I see how the query optimizer is evaluating my query?
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Sun Jun 23 17:16:13 EDT 2002</P>
+ <P>Last updated: Mon Jun 24 21:45:50 EDT 2002</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
<PRE>
SELECT col
FROM tab
- ORDER BY col
+ ORDER BY col [ DESC ]
LIMIT 1
</PRE>
<P>When using wild-card operators such as <SMALL>LIKE</SMALL> or
- <I>~</I>, indexes can only be used if the beginning of the search
+ <I>~</I>, indexes can only be used if the default C local is used
+during initdb and the beginning of the search
is anchored to the start of the string. Therefore, to use indexes,
<SMALL>LIKE</SMALL> patterns must not start with <I>%</I>, and
<I>~</I>(regular expression) patterns must start with <I>^</I>.</P>