| PostgreSQL 8.2.6 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 bit-string value to bit( n ) , it will be truncated or zero-padded on the right to be exactly n bits, without raising an error. Similarly, if one explicitly casts a bit-string 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. Bit-logical operators and string manipulation functions are available; see Section 9.6 .
Example 8-3. 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