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v3.0

Documentation:v3.0

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Bit String Functions and Operators

Aside from the usual comparison operators, the following operators can be used. Bit string operands of &, |, and # must be of equal length. In case of bit shifting, the original length of the string is preserved by zero padding (if necessary).

  • ||

    Description: Connects bit strings.

    Example:

    MogDB=# SELECT B'10001' || B'011' AS RESULT;
      result
    ----------
     10001011
    (1 row)

    img NOTE: It is recommended that a column have no more than 180 consecutive internal joins. A column with over 180 joins will be split into joined consecutive strings. Example:str1||str2||str3||str4 is split into (str1||str2)||(str3||str4).

  • &

    Description: Specifies the AND operation between bit strings.

    Example:

    MogDB=# SELECT B'10001' & B'01101' AS RESULT;
     result
    --------
     00001
    (1 row)
  • |

    Description: Specifies the OR operation between bit strings.

    Example:

    MogDB=# SELECT B'10001' | B'01101' AS RESULT;
     result
    --------
     11101
    (1 row)
  • #

    Description: Specifies the OR operation between bit strings if they are inconsistent. If the same positions in the two bit strings are both 1 or 0, the position returns 0.

    Example:

    MogDB=# SELECT B'10001' # B'01101' AS RESULT;
     result
    --------
     11100
    (1 row)
  • ~

    Description: Specifies the NOT operation between bit strings.

    Example:

    MogDB=# SELECT ~B'10001'AS RESULT;
     result
    ----------
     01110
    (1 row)
  • <<

    Description: Shifts left in a bit string.

    Example:

    MogDB=# SELECT B'10001' << 3 AS RESULT;
     result
    ----------
     01000
    (1 row)
  • >>

    Description: Shifts right in a bit string.

    Example:

    MogDB=# SELECT B'10001' >> 2 AS RESULT;
     result
    ----------
     00100
    (1 row)

The following SQL-standard functions work on bit strings as well as strings:length, bit_length, octet_length, position, substring, and overlay.

The following functions work on bit strings as well as binary strings:get_bit and set_bit. When working with a bit string, these functions number the first (leftmost) bit of the string as bit 0.

In addition, it is possible to convert between integral values and type bit. Example:

MogDB=# SELECT 44::bit(10) AS RESULT;
   result
------------
 0000101100
(1 row)

MogDB=# SELECT 44::bit(3) AS RESULT;
 result
--------
 100
(1 row)

MogDB=# SELECT cast(-44 as bit(12)) AS RESULT;
    result
--------------
 111111010100
(1 row)

MogDB=# SELECT '1110'::bit(4)::integer AS RESULT;
 result
--------
     14
(1 row)

MogDB=# select substring('10101111'::bit(8), 2);
 substring
-----------
 0101111
(1 row)

img NOTE: Casting to just "bit" means casting to bit(1), and so will deliver only the least significant bit of the integer.

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