在CREATE TABLE student
(
SNO CHAR(7) NOT NULL,
SNAME VARCHAR(8) NOT NULL,
SEX CHAR(2) NOT NULL,
BDATE DATE NOT NULL,
HEIGHT DEC(3,2) DEFAULT 0.00,
PRIMARY KEY(SNO),
CHECK (HEIGHT>0)
);中, PRIMARY KEY(SNO) 是()
A.域完整性約束
B.實體完整性約束
C.引用完整性約束
D.固有約束