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.
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 it 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.
