Jincang database kingbasees SQL language reference manual (3.1.1.6. boolean type, 3.1.1.7. bit string type)

3.1.1.6.  Boolean type

grammar ：BOOLEAN

KingbaseES Provide standard SQL type BOOLEAN. BOOLEAN The value is “true（ really ）”、“false（ false ）” And the third state “unknown（ Unknown ）”, The unknown state is determined by SQL A null value means .

data type	describe
BOOLEAN	Said really 、 Fake data type .1 Byte storage .

3.1.1.7.  Bit string type

A bit string is a string 1 and 0 String of .

3.1.1.7.1. BIT type

grammar ：BIT[(n)]

n It's a positive integer. , The data must match the length accurately “n“, If you store a shorter or longer bit string, an error will be reported .n default , The default is 1.

3.1.1.7.2. BIT VAYRING type

grammar ：BIT VAYRING(n)

Variable length bit string , The longest is n,n It's a positive integer. . If the storage exceeds n False report .n default , Indicates that the type has no length limit .

Be careful

If we explicitly convert a bit string value to bit(n), Then its right side will be truncated or zero filled on the right , Until just ``n`` position , And will not throw any errors . Similarly , If we explicitly convert a bit string value to bit varying(n), If it exceeds ``n`` position , Then its right side will be truncated .

Please refer to   Bit string constant   Get information about the syntax of bit string constants . There are also some bit logic operators and string manipulation functions available , see   Bit string functions and operators  .

example 10-1. Use bit string type

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

A bit string value for each 8 The group of bits requires a byte , Plus total 5 Or 8 Bytes , It depends on the length of the string （ But long values may be compressed or moved out of line , Such as   Character type   The interpretation of string in is the same ）.