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Make discussion of names clearer and more accurate.

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This commit is contained in:
Tom Lane 2000-03-30 23:42:34 +00:00
parent 996bc5358c
commit 175dbf741b
1 changed files with 19 additions and 7 deletions
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doc/src/sgml/syntax.sgml
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@ -340,17 +340,23 @@ A comment beginning with "/*" extends to the first occurrence of "*/".
<title>Names</title> <title>Names</title>
<para> <para>
Names in SQL are sequences of less than NAMEDATALEN alphanumeric characters, Names in SQL must begin with a letter
starting with an alphabetic character. By default, NAMEDATALEN is set (<literal>a</literal>-<literal>z</literal>) or underscore
to 32 (but at the time the system is built, NAMEDATALEN can be changed (<literal>_</literal>).
by changing the <literal>#define</literal> in Subsequent characters in a name can be letters, digits
src/backend/include/postgres.h). (<literal>0</literal>-<literal>9</literal>),
Underscore ("_") is considered an alphabetic character. or underscores. The system uses no more than NAMEDATALEN-1 characters
of a name; longer names can be written in queries, but they will be
truncated.
By default, NAMEDATALEN is 32 so the maximum name length is 31 (but
at the time the system is built, NAMEDATALEN can be changed in
src/include/postgres_ext.h).
</para> </para>
<para> <para>
Names containing other characters may be formed by surrounding them Names containing other characters may be formed by surrounding them
with double quotes. For example, table or column names may contain with double quotes (<literal>"</literal>). For example, table or column
names may contain
otherwise disallowed characters such as spaces, ampersands, etc. if otherwise disallowed characters such as spaces, ampersands, etc. if
quoted. Quoting a name also makes it case-sensitive, quoted. Quoting a name also makes it case-sensitive,
whereas unquoted names are always folded to lower case. For example, whereas unquoted names are always folded to lower case. For example,
@ -359,6 +365,12 @@ A comment beginning with "/*" extends to the first occurrence of "*/".
considered the same by <productname>Postgres</productname>, but considered the same by <productname>Postgres</productname>, but
<literal>"Foo"</literal> is a different name. <literal>"Foo"</literal> is a different name.
</para> </para>
<para>
Double quotes can also be used to protect a name that would otherwise
be taken to be an SQL keyword. For example, <literal>IN</literal>
is a keyword but <literal>"IN"</literal> is a name.
</para>
</sect1> </sect1>
<sect1> <sect1>