

PostgreSQL 8.2.6 Documentation  

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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 910 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 910. 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 SQLstandard 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 signextend on the left.