Bit String Functions and Operators

PostgreSQL 9.3.5 Documentation
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# 9.6. Bit String Functions and Operators

This section describes functions and operators for examining and manipulating bit strings, that is values of the types `bit` and `bit varying`. Aside from the usual comparison operators, the operators shown in Table 9-10 can be used. Bit string operands of `&`, `|`, and `#` must be of equal length. When bit shifting, the original length of the string is preserved, as shown in the examples.

Table 9-10. Bit String Operators

Operator | Description | Example | Result
--- | --- | --- | ---
`||` | concatenation | `B'10001' || B'011'` | `10001011`
`&` | bitwise AND | `B'10001' & B'01101'` | `00001`
`|` | bitwise OR | `B'10001' | B'01101'` | `11101`
`#` | bitwise XOR | `B'10001' # B'01101'` | `11100`
`~` | bitwise NOT | `~ B'10001'` | `01110`
`<<` | bitwise shift left | `B'10001' << 3` | `01000`
`>>` | bitwise shift right | `B'10001' >> 2` | `00100`

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

The following functions work on bit strings as well as binary strings: ``get_bit``, ``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 cast integral values to and from type `bit`. Some examples:

    44::bit(10)                    0000101100
    44::bit(3)                     100
    cast(-44 as bit(12))           111111010100
    '1110'::bit(4)::integer        14

Note that casting to just "bit" means casting to `bit(1)`, and so will deliver only the least significant bit of the integer.

> Note: Prior to PostgreSQL 8.0, casting an integer to `bit(n)` would copy the leftmost `n` bits of the integer, whereas now it copies the rightmost `n` bits. Also, casting an integer to a bit string width wider than the integer itself will sign-extend on the left.

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