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<chapter id="datatype">

<entry>binary data</entry>

</row>

<row>

<entry><type>character(<replaceable>n</replaceable>)</type></entry>

<entry><type>char(<replaceable>n</replaceable>)</type></entry>

<entry>fixed-length character string</entry>

</row>

<row>

<entry><type>character varying(<replaceable>n</replaceable>)</type></entry>

<entry><type>varchar(<replaceable>n</replaceable>)</type></entry>

<entry>variable-length character string</entry>

</row>

<row>

<entry><type>character(<replaceable>n</replaceable>)</type></entry>

<entry><type>char(<replaceable>n</replaceable>)</type></entry>

<entry>fixed-length character string</entry>

</row>

<row>

<entry><type>cidr</type></entry>

<entry></entry>

The following types (or spellings thereof) are specified by

<acronym>SQL</acronym>: <type>bit</type>, <type>bit

varying</type>, <type>boolean</type>, <type>char</type>,

<type>character</type>, <type>character varying</type>,

<type>character varying</type>, <type>character</type>,

<type>varchar</type>, <type>date</type>, <type>double

precision</type>, <type>integer</type>, <type>interval</type>,

<type>numeric</type>, <type>decimal</type>, <type>real</type>,

</row>

</thead>

<tbody>

<row>

<entry><type>character(<replaceable>n</>)</type>, <type>char(<replaceable>n</>)</type></entry>

<entry>fixed-length, blank padded</entry>

</row>

<row>

<entry><type>character varying(<replaceable>n</>)</type>, <type>varchar(<replaceable>n</>)</type></entry>

<entry>variable-length with limit</entry>

</row>

<row>

<entry><type>character(<replaceable>n</>)</type>, <type>char(<replaceable>n</>)</type></entry>

<entry>fixed-length, blank padded</entry>

</row>

<row>

<entry><type>text</type></entry>

<entry>variable unlimited length</entry>

<para>

<acronym>SQL</acronym> defines two primary character types:

<type>character(<replaceable>n</>)</type> and <type>character

varying(<replaceable>n</>)</type>, where <replaceable>n</> is a

positive integer. Both of these types can store strings up to

<type>character varying(<replaceable>n</>)</type> and

<type>character(<replaceable>n</>)</type>, where <replaceable>n</>

is apositive integer. Both of these types can store strings up to

<replaceable>n</> characters in length. An attempt to store a

longer string into a column of these types will result in an

error, unless the excess characters are all spaces, in which case

the string will be truncated to the maximum length.(This

somewhatbizarre exception is required by the

<acronym>SQL</acronym>standard.)If the string to be stored is

shorter than the declaredlength, values of type

<type>character</type> willbe space-padded; values of type

<type>character varying</type> will simply store theshorter

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

length, values of type <type>character</type> will be space-padded;

values of type<type>character varying</type> willsimply store the

shorter

string.

</para>

<note>

<para>

If one explicitly casts a value to

<type>character(<replaceable>n</>)</type> or <type>character

varying(<replaceable>n</>)</type>, then anoverlength value will

be truncated to <replaceable>n</> characters without raising an

error.(This too is required by the <acronym>SQL</acronym>

standard.)

If one explicitly casts a value to <type>character

varying(<replaceable>n</>)</type> or

<type>character(<replaceable>n</>)</type>, then anover-length

value willbe truncated to <replaceable>n</> characters without

raising anerror. (This too is required by the

<acronym>SQL</acronym>standard.)

</para>

</note>

</note>

<para>

The notations <type>char(<replaceable>n</>)</type> and

<type>varchar(<replaceable>n</>)</type> are aliases for

<type>character(<replaceable>n</>)</type> and <type>character

varying(<replaceable>n</>)</type>,

respectively.<type>character</type> without length specifier is

equivalent to<type>character(1)</type>; if <type>character

varying</type> is usedwithout length specifier, the type accepts

strings of any size. Thelatter is a <productname>PostgreSQL</> extension.

The notations <type>varchar(<replaceable>n</>)</type> and

<type>char(<replaceable>n</>)</type> are aliases for <type>character

varying(<replaceable>n</>)</type> and

<type>character(<replaceable>n</>)</type>, respectively.

<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</> extension.

</para>

<para>

<para>

There are two other fixed-length character types in

<productname>PostgreSQL</productname>, shown in <xref linkend="datatype-character-special-table">.

The <type>name</type> type

exists <emphasis>only</emphasis> for storage of internal catalog

names and is not intended for use by the general user. Its length

is currently defined as 64 bytes (63 usable characters plus terminator)

but should be referenced using the constant

<symbol>NAMEDATALEN</symbol>. The length is set at compile time

(and is therefore adjustable for special uses); the default

maximum length may change in a future release. The type

<type>"char"</type> (note the quotes) is different from

<type>char(1)</type> in that it only uses one byte of storage. It

is internally used in the system catalogs as a poor-man's

enumeration type.

<productname>PostgreSQL</productname>, shown in <xref

linkend="datatype-character-special-table">. The <type>name</type>

type exists <emphasis>only</emphasis> for storage of internal

catalog names and is not intended for use by the general user. Its

length is currently defined as 64 bytes (63 usable characters plus

terminator) but should be referenced using the constant

<symbol>NAMEDATALEN</symbol>. The length is set at compile time (and

is therefore adjustable for special uses); the default maximum

length may change in a future release. The type <type>"char"</type>

(note the quotes) is different from <type>char(1)</type> in that it

only uses one byte of storage. It is internally used in the system

catalogs as a poor-man's enumeration type.

</para>

<table id="datatype-character-special-table">

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<chapter id="sql">

<listitem>

<para>

CHAR(<replaceable class="parameter">n</replaceable>):

fixed length character string of length

VARCHAR(<replaceable class="parameter">n</replaceable>):

varying length character string of maximum length

<replaceable class="parameter">n</replaceable>.

</para>

</listitem>

<listitem>

<para>

VARCHAR(<replaceable class="parameter">n</replaceable>):

varying length character string of maximum length

CHAR(<replaceable class="parameter">n</replaceable>):

fixed length character string of length

<replaceable class="parameter">n</replaceable>.

</para>

</listitem>

</itemizedlist>

</para>

</sect3>