8.10. 位元字串型別
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Bit strings are strings of 1's and 0's. They can be used to store or visualize bit masks. There are two SQL bit types:bit(n)andbit varying(n), wherenis a positive integer.
bittype data must match the lengthnexactly; it is an error to attempt to store shorter or longer bit strings.bit varyingdata is of variable length up to the maximum lengthn; longer strings will be rejected. Writingbitwithout a length is equivalent tobit(1), whilebit varyingwithout a length specification means unlimited length.
Note:If one explicitly casts a bit-string value tobit(n), it will be truncated or zero-padded on the right to be exactlynbits, without raising an error. Similarly, if one explicitly casts a bit-string value tobit varying(n), it will be truncated on the right if it is more thannbits.
Refer tofor information about the syntax of bit string constants. Bit-logical operators and string manipulation functions are available; see.
Example 8-3. Using the Bit String Types
A bit string value requires 1 byte for each group of 8 bits, plus 5 or 8 bytes overhead depending on the length of the string (but long values may be compressed or moved out-of-line, as explained infor character strings).