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Add mention of functional indexes for case-insensitive comparisons.

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Bruce Momjian
2001-05-07 19:58:31 +00:00
parent 465cf168eb
commit 5fdae774a1
1 changed files with 19 additions and 2 deletions
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doc/src/FAQ/FAQ.html
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@ -112,7 +112,8 @@
<A href="#4.11">4.11</A>) What is an R-tree index?<BR> <A href="#4.11">4.11</A>) What is an R-tree index?<BR>
<A href="#4.12">4.12</A>) What is the Genetic Query Optimizer?<BR> <A href="#4.12">4.12</A>) What is the Genetic Query Optimizer?<BR>
<A href="#4.13">4.13</A>) How do I perform regular expression <A href="#4.13">4.13</A>) How do I perform regular expression
searches and case-insensitive regular expression searches?<BR> searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?<BR>
<A href="#4.14">4.14</A>) In a query, how do I detect if a field <A href="#4.14">4.14</A>) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>?<BR> is <SMALL>NULL</SMALL>?<BR>
<A href="#4.15">4.15</A>) What is the difference between the <A href="#4.15">4.15</A>) What is the difference between the
@ -957,13 +958,29 @@ Maximum number of indexes on a table? unlimited
search.</P> search.</P>
<H4><A name="4.13">4.13</A>) How do I perform regular expression <H4><A name="4.13">4.13</A>) How do I perform regular expression
searches and case-insensitive regular expression searches?</H4> searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?</H4>
<P>The <I>~</I> operator does regular expression matching, and <P>The <I>~</I> operator does regular expression matching, and
<I>~*</I> does case-insensitive regular expression matching. The <I>~*</I> does case-insensitive regular expression matching. The
case-insensitive variant of <SMALL>LIKE</SMALL> is called case-insensitive variant of <SMALL>LIKE</SMALL> is called
<SMALL>ILIKE</SMALL> in PostgreSQL 7.1 and later.</P> <SMALL>ILIKE</SMALL> in PostgreSQL 7.1 and later.</P>
<P>Case-insensitive equality comparisons are normally expressed as:
<PRE>
SELECT *
FROM tab
WHERE lower(col) = 'abc'
</PRE>
This will not use an standard index. However, if you create a
functional index, it will be used:
<PRE>
CREATE INDEX tabindex on tab (lower(col));
</PRE>
<H4><A name="4.14">4.14</A>) In a query, how do I detect if a field <H4><A name="4.14">4.14</A>) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>?</H4> is <SMALL>NULL</SMALL>?</H4>