| PostgreSQL 9.2.4 Documentation | ||||
|---|---|---|---|---|
| Prev | Up | Chapter 9. Functions and Operators | Next | |
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.
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.
Proceed to the comment form.