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 9.13 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 9.13. Bit String Operators
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
.
When working with a bit string, these functions number the first
(leftmost) bit of the string as bit 0.
set_bit
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.
Casting an integer to bit(n)
copies the rightmost
n
bits. Casting an integer to a bit string width wider
than the integer itself will sign-extend on the left.