diff options
| -rw-r--r-- | doc/src/sgml/datatype.sgml | 59 |
1 files changed, 36 insertions, 23 deletions
diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index 0258b192e0e..b030b36002f 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -1154,6 +1154,10 @@ SELECT '52093.89'::money::numeric::float8; <primary>varchar</primary> </indexterm> + <indexterm zone="datatype-character"> + <primary>bpchar</primary> + </indexterm> + <table id="datatype-character-table"> <title>Character Types</title> <tgroup cols="2"> @@ -1169,7 +1173,7 @@ SELECT '52093.89'::money::numeric::float8; <entry>variable-length with limit</entry> </row> <row> - <entry><type>character(<replaceable>n</replaceable>)</type>, <type>char(<replaceable>n</replaceable>)</type></entry> + <entry><type>character(<replaceable>n</replaceable>)</type>, <type>char(<replaceable>n</replaceable>)</type>, <type>bpchar(<replaceable>n</replaceable>)</type></entry> <entry>fixed-length, blank padded</entry> </row> <row> @@ -1196,7 +1200,14 @@ SELECT '52093.89'::money::numeric::float8; error, unless the excess characters are all spaces, in which case the string will be truncated to the maximum length. (This somewhat bizarre exception is required by the <acronym>SQL</acronym> - standard.) If the string to be stored is shorter than the declared + standard.) + However, if one explicitly casts a value to <type>character + varying(<replaceable>n</replaceable>)</type> or + <type>character(<replaceable>n</replaceable>)</type>, then an over-length + value will be truncated to <replaceable>n</replaceable> characters without + raising an error. (This too is required by the + <acronym>SQL</acronym> standard.) + If the string to be stored is shorter than the declared length, values of type <type>character</type> will be space-padded; values of type <type>character varying</type> will simply store the shorter @@ -1204,33 +1215,35 @@ SELECT '52093.89'::money::numeric::float8; </para> <para> - If one explicitly casts a value to <type>character - varying(<replaceable>n</replaceable>)</type> or - <type>character(<replaceable>n</replaceable>)</type>, then an over-length - value will be truncated to <replaceable>n</replaceable> characters without - raising an error. (This too is required by the - <acronym>SQL</acronym> standard.) + In addition, <productname>PostgreSQL</productname> provides the + <type>text</type> type, which stores strings of any length. + Although the <type>text</type> type is not in the + <acronym>SQL</acronym> standard, several other SQL database + management systems have it as well. + <type>text</type> is <productname>PostgreSQL</productname>'s native + string data type, in that most built-in functions operating on strings + are declared to take or return <type>text</type> not <type>character + varying</type>. For many purposes, <type>character varying</type> + acts as though it were a <link linkend="domains">domain</link> + over <type>text</type>. </para> <para> - The notations <type>varchar(<replaceable>n</replaceable>)</type> and - <type>char(<replaceable>n</replaceable>)</type> are aliases for <type>character - varying(<replaceable>n</replaceable>)</type> and - <type>character(<replaceable>n</replaceable>)</type>, respectively. - If specified, the length must be greater than zero and cannot exceed - 10485760. - <type>character</type> without length specifier is equivalent to - <type>character(1)</type>. If <type>character varying</type> is used - without length specifier, the type accepts strings of any size. The - latter is a <productname>PostgreSQL</productname> extension. + The type name <type>varchar</type> is an alias for <type>character + varying</type>, while <type>char</type> and <type>bpchar</type> are + aliases for <type>character</type>. + The <type>varchar</type> and <type>char</type> aliases are defined in + the <acronym>SQL</acronym> standard, but <type>bpchar</type> is + a <productname>PostgreSQL</productname> extension. </para> <para> - In addition, <productname>PostgreSQL</productname> provides the - <type>text</type> type, which stores strings of any length. - Although the type <type>text</type> is not in the - <acronym>SQL</acronym> standard, several other SQL database - management systems have it as well. + If specified, the length <replaceable>n</replaceable> must be greater + than zero and cannot exceed 10485760. + <type>character</type> without length specifier is equivalent to + <type>character(1)</type>. If <type>character varying</type> is used + without length specifier, the type accepts strings of any size. The + latter behavior is a <productname>PostgreSQL</productname> extension. </para> <para> |