CREATE TABLE `employees` (
`id` int(11) NOT NULL AUTO_INCREMENT, 
`name` varchar(24) NOT NULL DEFAULT '' COMMENT '姓名', 
`age` int(11) NOT NULL DEFAULT '0' COMMENT '年龄', 
`position` varchar(20) NOT NULL DEFAULT '' COMMENT '职位', 
`hire_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '入职时间', 
PRIMARY KEY (`id`), 
KEY `idx_name_age_position` (`name`,`age`,`position`) USING BTREE ) 
ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COMMENT='员工记录表'; 
INSERT INTO employees(name,age,position,hire_time) VALUES('LiLei',22,'manager',NOW()); 
INSERT INTO employees(name,age,position,hire_time) VALUES('HanMeimei', 23,'dev',NOW()); 
INSERT INTO employees(name,age,position,hire_time) VALUES('Lucy',23,'dev',NOW());

EXPLAIN SELECT * FROM employees WHERE name= 'LiLei';
EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age = 22;
EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age = 22 AND position ='manage r';

# 第一条匹配成功
EXPLAIN SELECT * FROM employees WHERE name = 'Bill' and age = 31; 
# 第二、三条匹配失败,带头大哥不在
EXPLAIN SELECT * FROM employees WHERE age = 30 AND position = 'dev'; 
EXPLAIN SELECT * FROM employees WHERE position = 'manager';