主键索引
CREATE TABLE TEST( a int primary key, b int, c int, d int, e char(1) )engine=INNODB INSERT INTO TEST VALUES(4,3,1,1,'d') INSERT INTO TEST VALUES(1,1,1,1,'a') INSERT INTO TEST VALUES(8,8,8,8,'h') INSERT INTO TEST VALUES(2,2,2,2,'b') INSERT INTO TEST VALUES(5,2,3,5,'e') INSERT INTO TEST VALUES(3,3,2,2,'c') INSERT INTO TEST VALUES(7,4,5,5,'g') INSERT INTO TEST VALUES(6,6,4,4,'f')
B+树结构