9.6. 二元字串函式及運算子
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 9.14 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 9.14. 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
, 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:
Note that casting to just “bit” means casting to bit(1)
, and so will deliver only the least significant bit of the integer.
Note
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.\
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