This documentation is for an unsupported version of PostgreSQL.
You may want to view the same page for the
current
version, or one of the other supported versions listed above instead.
This section describes functions and operators for examining
and manipulating binary string values. Strings in this context
mean values of the type BYTEA.
SQL defines some string
functions with a special syntax where certain key words rather
than commas are used to separate the arguments. Details are in
Table
6-9. Some functions are also implemented using the regular
syntax for function invocation. (See Table
6-10.)
Table 6-9. SQL
Binary String Functions and Operators
| Function |
Return Type |
Description |
Example |
Result |
string || string |
bytea |
String concatenation |
'\\\\Post'::bytea ||
'\\047greSQL\\000'::bytea |
\\Post'greSQL\000 |
octet_length(string) |
integer |
Number of bytes in binary string |
octet_length('jo\\000se'::bytea) |
5 |
position(substring in string) |
integer |
Location of specified substring |
position('\\000om'::bytea in
'Th\\000omas'::bytea) |
3 |
substring(string [from
integer] [for integer]) |
bytea |
Extract substring |
substring('Th\\000omas'::bytea
from 2 for 3) |
h\000o |
trim([both] characters from string) |
bytea |
Remove the longest string containing only the
characters from the
beginning/end/both ends of the string |
trim('\\000'::bytea from
'\\000Tom\\000'::bytea) |
Tom |
get_byte(string, offset) |
integer |
Extract byte from string. |
get_byte('Th\\000omas'::bytea,
4) |
109 |
set_byte(string, offset, newvalue) |
bytea |
Set byte in string. |
set_byte('Th\\000omas'::bytea, 4,
64) |
Th\000o@as |
get_bit(string, offset) |
integer |
Extract bit from string. |
get_bit('Th\\000omas'::bytea,
45) |
1 |
set_bit(string, offset, newvalue) |
bytea |
Set bit in string. |
set_bit('Th\\000omas'::bytea, 45,
0) |
Th\000omAs |
Additional binary string manipulation functions are available
and are listed in Table
6-10. Some of them are used internally to implement the
SQL-standard string functions
listed in Table
6-9.
Table 6-10. Other Binary String Functions
| Function |
Return Type |
Description |
Example |
Result |
btrim(string bytea
trim bytea) |
bytea |
Remove (trim) the longest string consisting only of
characters in trim from
the start and end of string. |
btrim('\\000trim\\000'::bytea,'\\000'::bytea) |
trim |
length(string) |
integer |
Length of binary string |
length('jo\\000se'::bytea) |
5 |
encode(string bytea,
type text) |
text |
Encode binary string to ASCII-only representation. Supported
types are: base64, hex, escape. |
encode('123\\000456'::bytea,
'escape') |
123\000456 |
decode(string text,
type text) |
bytea |
Decode binary string from string previously encoded with
encode(). Parameter type is same
as in encode(). |
decode('123\\000456',
'escape') |
123\000456 |