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Updated on 2023-10-23 GMT+08:00
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Binary String Functions and Operators

String Operators

SQL defines some string functions that use keywords, rather than commas, to separate arguments.

  • octet_length(string)

    Description: Specifies the number of bytes in a binary string.

    Return type: int

    Example:

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    openGauss=# SELECT octet_length(E'jo\\000se'::bytea) AS RESULT;
 result
--------
      5
(1 row)
  • overlay(string placing string from int [for int])

    Description: Replaces substrings.

    Return type: bytea

    Example:

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    openGauss=# SELECT overlay(E'Th\\000omas'::bytea placing E'\\002\\003'::bytea from 2 for 3) AS RESULT;
     result     
----------------
 \x5402036d6173
(1 row)
  • position(substring in string)

    Description: Specifies the location of a specified substring.

    Return type: int

    Example:

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    openGauss=# SELECT position(E'\\000om'::bytea in E'Th\\000omas'::bytea) AS RESULT;
 result
--------
      3
(1 row)
  • substring(string [from int] [for int])

    Description: Truncates a substring.

    Return type: bytea

    Example:

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    openGauss=# SELECT substring(E'Th\\000omas'::bytea from 2 for 3) AS RESULT; 
  result  
----------
 \x68006f
(1 row)
  • substr(string, from int [, for int])

    Description: Truncates a substring.

    Return type: bytea

    Example:

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    openGauss=# select substr(E'Th\\000omas'::bytea,2, 3) as result;
  result
----------
 \x68006f
(1 row)
  • trim([both] bytes from string)

    Description: Removes the longest string containing only bytes from bytes from the start and end of string.

    Return type: bytea

    Example:

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    openGauss=# SELECT trim(E'\\000'::bytea from E'\\000Tom\\000'::bytea) AS RESULT;
  result  
----------
 \x546f6d
(1 row)

Other Binary String Functions

GaussDB provides common syntax used for calling functions.

  • btrim(string bytea,bytes bytea)

    Description: Removes the longest string containing only bytes from bytes from the start and end of string.

    Return type: bytea

    Example:

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    openGauss=# SELECT btrim(E'\\000trim\\000'::bytea, E'\\000'::bytea) AS RESULT;
   result   
------------
 \x7472696d
(1 row)
  • get_bit(string, offset)

    Description: Extracts bits from a string.

    Return type: int

    Example:

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    openGauss=# SELECT get_bit(E'Th\\000omas'::bytea, 45) AS RESULT; 
 result
--------
      1
(1 row)
  • get_byte(string, offset)

    Description: Extracts bytes from a string.

    Return type: int

    Example:

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    openGauss=# SELECT get_byte(E'Th\\000omas'::bytea, 4) AS RESULT; 
 result
--------
    109
(1 row)
  • rawcmp

    Description: Specifies the raw data type comparison function.

    Parameter: raw, raw

    Return type: integer

  • raweq

    Description: Specifies the raw data type comparison function.

    Parameter: raw, raw

    Return type: Boolean

  • rawge

    Description: Specifies the raw data type comparison function.

    Parameter: raw, raw

    Return type: Boolean

  • rawgt

    Description: Specifies the raw data type comparison function.

    Parameter: raw, raw

    Return type: Boolean

  • rawin

    Description: Specifies the raw data type parsing function.

    Parameter: cstring

    Return type: bytea

  • rawle

    Description: Specifies the raw data type parsing function.

    Parameter: raw, raw

    Return type: Boolean

  • rawlike

    Description: Specifies the raw data type parsing function.

    Parameter: raw, raw

    Return type: Boolean

  • rawlt

    Description: Specifies the raw data type parsing function.

    Parameter: raw, raw

    Return type: Boolean

  • rawne

    Description: Compares whether the raw types are the same.

    Parameter: raw, raw

    Return type: Boolean

  • rawnlike

    Description: Checks whether the raw type matches the mode.

    Parameter: raw, raw

    Return type: Boolean

  • rawout

    Description: Specifies the RAW output API.

    Parameter: bytea

    Return type: cstring

  • rawsend

    Description: Converts the bytea type to the binary type.

    Parameter: raw

    Return type: bytea

  • rawtohex

    Description: Converts the raw format to the hexadecimal format.

    Parameter: text

    Return type: text

  • set_bit(string,offset, newvalue)

    Description: Sets bits in a string.

    Return type: bytea

    Example:

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    openGauss=# SELECT set_bit(E'Th\\000omas'::bytea, 45, 0) AS RESULT; 
      result      
------------------
 \x5468006f6d4173
(1 row)
  • set_byte(string,offset, newvalue)

    Description: Sets bytes in a string.

    Return type: bytea

    Example:

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    openGauss=# SELECT set_byte(E'Th\\000omas'::bytea, 4, 64) AS RESULT; 
      result      
------------------
 \x5468006f406173
(1 row)
Parent topic: Functions and Operators