Text Size: Normal / Large

Home → Documentation → Manuals → PostgreSQL 8.2

PostgreSQL 8.2.3 Documentation
Prev	Fast Backward	Chapter 9. Functions and Operators	Fast Forward	Next

9.5. Binary String Functions and Operators

This section describes functions and operators for examining and manipulating values of 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 9-8. Some functions are also implemented using the regular syntax for function invocation. (See Table 9-9.)

Table 9-8. SQL Binary String Functions and Operators

Function	Return Type	Description	Example	Result
`string \|\| string`	`bytea`	String concatenation	`E'\\\\Post'::bytea \|\| E'\\047gres\\000'::bytea`	`\\Post'gres\000`
`get_bit`(`string`, `offset`)	`int`	Extract bit from string	`get_bit(E'Th\\000omas'::bytea, 45)`	`1`
`get_byte`(`string`, `offset`)	`int`	Extract byte from string	`get_byte(E'Th\\000omas'::bytea, 4)`	`109`
`octet_length(string)`	`int`	Number of bytes in binary string	`octet_length( E'jo\\000se'::bytea)`	`5`
`position(substring in string)`	`int`	Location of specified substring	`position(E'\\000om'::bytea in E'Th\\000omas'::bytea)`	`3`
`set_bit`(`string`, `offset`, `newvalue`)	`bytea`	Set bit in string	`set_bit(E'Th\\000omas'::bytea, 45, 0)`	`Th\000omAs`
`set_byte`(`string`, `offset`, `newvalue`)	`bytea`	Set byte in string	`set_byte(E'Th\\000omas'::bytea, 4, 64)`	`Th\000o@as`
`substring(string [from int] [for int])`	`bytea`	Extract substring	`substring(E'Th\\000omas'::bytea from 2 for 3)`	`h\000o`
`trim([both] bytes from string)`	`bytea`	Remove the longest string containing only the bytes in `bytes` from the start and end of `string`	`trim(E'\\000'::bytea from E'\\000Tom\\000'::bytea)`	`Tom`

Additional binary string manipulation functions are available and are listed in Table 9-9. Some of them are used internally to implement the SQL-standard string functions listed in Table 9-8.

Table 9-9. Other Binary String Functions

Function	Return Type	Description	Example	Result
`btrim(string bytea, bytes bytea)`	`bytea`	Remove the longest string consisting only of bytes in `bytes` from the start and end of `string`	`btrim(E'\\000trim\\000'::bytea, E'\\000'::bytea)`	`trim`
`decode(string text, type text)`	`bytea`	Decode binary string from `string` previously encoded with `encode`. Parameter type is same as in `encode`.	`decode(E'123\\000456', 'escape')`	`123\000456`
`encode(string bytea, type text)`	`text`	Encode binary string to ASCII-only representation. Supported types are: `base64`, `hex`, `escape`.	`encode(E'123\\000456'::bytea, 'escape')`	`123\000456`
`length(string)`	`int`	Length of binary string	`length(E'jo\\000se'::bytea)`	`5`
`md5(string)`	`text`	Calculates the MD5 hash of `string`, returning the result in hexadecimal	`md5(E'Th\\000omas'::bytea)`	`8ab2d3c9689aaf18 b4958c334c82d8b1`

Prev	Home	Next
String Functions and Operators	Up	Bit String Functions and Operators

User Comments

No comments could be found for this page.

Add Comment

Please use this form to add your own comments regarding your experience with particular features of PostgreSQL, clarifications of the documentation, or hints for other users. Please note, this is not a support forum, and your IP address will be logged. If you have a question or need help, please see the faq, try a mailing list, or join us on IRC. Note that submissions containing URLs or other keywords commonly found in 'spam' comments may be silently discarded. Please contact the webmaster if you think this is happening to you in error.

In order to submit a comment, you must have a community account.

* denotes required field