Table 8.4. Character Types
| Name | Description | 
|---|---|
| character varying(,varchar( | variable-length with limit | 
| character(,char( | fixed-length, blank padded | 
| text | variable unlimited length | 
Table 8.4 shows the general-purpose character types available in PostgreSQL.
    SQL defines two primary character types:
    character varying( and
    n)character(, where n)n
    is a positive integer.  Both of these types can store strings up to
    n characters (not bytes) 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 somewhat
    bizarre exception is required by the SQL
    standard.) If the string to be stored is shorter than the declared
    length, values of type character will be space-padded;
    values of type character varying will simply store the
    shorter
    string.
   
    If one explicitly casts a value to character
    varying( or
    n)character(, then an over-length
    value will be truncated to n)n characters without
    raising an error. (This too is required by the
    SQL standard.)
   
    The notations varchar( and
    n)char( are aliases for n)character
    varying( and
    n)character(, respectively.
    n)character without length specifier is equivalent to
    character(1). If character varying is used
    without length specifier, the type accepts strings of any size. The
    latter is a PostgreSQL extension.
   
    In addition, PostgreSQL provides the
    text type, which stores strings of any length.
    Although the type text is not in the
    SQL standard, several other SQL database
    management systems have it as well.
   
    Values of type character are physically padded
    with spaces to the specified width n, and are
    stored and displayed that way.  However, trailing spaces are treated as
    semantically insignificant and disregarded when comparing two values
    of type character.  In collations where whitespace
    is significant, this behavior can produce unexpected results;
    for example SELECT 'a '::CHAR(2) collate "C" <
    E'a\n'::CHAR(2) returns true, even though C
    locale would consider a space to be greater than a newline.
    Trailing spaces are removed when converting a character value
    to one of the other string types.  Note that trailing spaces
    are semantically significant in
    character varying and text values, and
    when using pattern matching, that is LIKE and
    regular expressions.
   
The characters that can be stored in any of these data types are determined by the database character set, which is selected when the database is created. Regardless of the specific character set, the character with code zero (sometimes called NUL) cannot be stored. For more information refer to Section 23.3.
    The storage requirement for a short string (up to 126 bytes) is 1 byte
    plus the actual string, which includes the space padding in the case of
    character.  Longer strings have 4 bytes of overhead instead
    of 1.  Long strings are compressed by the system automatically, so
    the physical requirement on disk might be less. Very long values are also
    stored in background tables so that they do not interfere with rapid
    access to shorter column values. In any case, the longest
    possible character string that can be stored is about 1 GB. (The
    maximum value that will be allowed for n in the data
    type declaration is less than that. It wouldn't be useful to
    change this because with multibyte character encodings the number of
    characters and bytes can be quite different. If you desire to
    store long strings with no specific upper limit, use
    text or character varying without a length
    specifier, rather than making up an arbitrary length limit.)
   
     There is no performance difference among these three types,
     apart from increased storage space when using the blank-padded
     type, and a few extra CPU cycles to check the length when storing into
     a length-constrained column.  While
     character( has performance
     advantages in some other database systems, there is no such advantage in
     PostgreSQL; in fact
     n)character( is usually the slowest of
     the three because of its additional storage costs.  In most situations
     n)text or character varying should be used
     instead.
    
Refer to Section 4.1.2.1 for information about the syntax of string literals, and to Chapter 9 for information about available operators and functions.
Example 8.1. Using the Character Types
CREATE TABLE test1 (a character(4));
INSERT INTO test1 VALUES ('ok');
SELECT a, char_length(a) FROM test1; -- (1)
  a   | char_length
------+-------------
 ok   |           2
CREATE TABLE test2 (b varchar(5));
INSERT INTO test2 VALUES ('ok');
INSERT INTO test2 VALUES ('good      ');
INSERT INTO test2 VALUES ('too long');
ERROR:  value too long for type character varying(5)
INSERT INTO test2 VALUES ('too long'::varchar(5)); -- explicit truncation
SELECT b, char_length(b) FROM test2;
   b   | char_length
-------+-------------
 ok    |           2
 good  |           5
 too l |           5
| 
       The  | 
    There are two other fixed-length character types in
    PostgreSQL, shown in Table 8.5. The name
    type exists only for the storage of identifiers
    in the internal system catalogs 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
    NAMEDATALEN in C source code.
    The length is set at compile time (and
    is therefore adjustable for special uses); the default maximum
    length might change in a future release. The type "char"
    (note the quotes) is different from char(1) in that it
    only uses one byte of storage. It is internally used in the system
    catalogs as a simplistic enumeration type.
   
Table 8.5. Special Character Types
| Name | Storage Size | Description | 
|---|---|---|
| "char" | 1 byte | single-byte internal type | 
| name | 64 bytes | internal type for object names |