

PostgreSQL 8.2.9 Documentation  

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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) and bit varying(n), where n is a positive integer.
bit type data must match the length n exactly; it is an error to attempt to store shorter or longer bit strings. bit varying data is of variable length up to the maximum length n; longer strings will be rejected. Writing bit without a length is equivalent to bit(1), while bit varying without a length specification means unlimited length.
Note: If one explicitly casts a bitstring value to bit(n), it will be truncated or zeropadded on the right to be exactly n bits, without raising an error. Similarly, if one explicitly casts a bitstring value to bit varying(n), it will be truncated on the right if it is more than n bits.
Refer to Section 4.1.2.3 for information about the syntax of bit string constants. Bitlogical operators and string manipulation functions are available; see Section 9.6.
Example 83. Using the bit string types
CREATE TABLE test (a BIT(3), b BIT VARYING(5)); INSERT INTO test VALUES (B'101', B'00'); INSERT INTO test VALUES (B'10', B'101'); ERROR: bit string length 2 does not match type bit(3) INSERT INTO test VALUES (B'10'::bit(3), B'101'); SELECT * FROM test; a  b + 101  00 100  101