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some clarifications inspired by the DocNotes

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This commit is contained in:
Peter Eisentraut 2001-08-07 22:41:49 +00:00
parent 2cb95cd925
commit e29c16dc50
1 changed files with 20 additions and 12 deletions
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32
doc/src/sgml/datatype.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.56 2001/06/18 19:05:11 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.57 2001/08/07 22:41:49 petere Exp $
-->
<chapter id="datatype">
@ -552,28 +552,24 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> (<replaceabl
<table tocentry="1">
<title>Character Types</title>
<tgroup cols="3">
<tgroup cols="2">
<thead>
<row>
<entry>Type Name</entry>
<entry>Storage</entry>
<entry>Type name</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>character(n), char(n)</entry>
<entry>(4+n) bytes</entry>
<entry>character(<replaceable>n</>), char(<replaceable>n</>)</entry>
<entry>Fixed-length blank padded</entry>
</row>
<row>
<entry>character varying(n), varchar(n)</entry>
<entry>(4+n) bytes</entry>
<entry>character varying(<replaceable>n</>), varchar(<replaceable>n</>)</entry>
<entry>Variable-length with limit</entry>
</row>
<row>
<entry>text</entry>
<entry>(4+n) bytes</entry>
<entry>Variable unlimited length</entry>
</row>
</tbody>
@ -624,9 +620,15 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> (<replaceabl
</para>
<para>
Refer to <xref linkend="sql-syntax-strings"> for information about
the syntax of string literals, and to <xref linkend="functions">
for information about available operators and functions.
The storage requirement for data of these types is 4 bytes plus
the actual string, and in case of <type>character</type> plus the
padding. Long strings will actually be compressed by the system
automatically. In any case, the longest possible character string
that can be stored is about 1 GB. (The maximum value that will be
allowed for <replaceable>n</> in the data type declaration is
actually larger than that. It wouldn't be very useful to change
this because with multi-byte character encodings the number of
characters and bytes can be quite different anyway.)
</para>
<tip>
@ -637,6 +639,12 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> (<replaceabl
</para>
</tip>
<para>
Refer to <xref linkend="sql-syntax-strings"> for information about
the syntax of string literals, and to <xref linkend="functions">
for information about available operators and functions.
</para>
<example>
<title>Using the character types</title>