mysql索引

1 先建表，插入数据，建索引，脚本如下：

--建表
create  table User(
                      id bigint auto_increment primary key,
                      name nvarchar(100),
                      age int,
                      position nvarchar(100)
);
--插入数据
INSERT INTO User (name, age, position)
SELECT
    CONCAT('User', FLOOR(RAND() * 100000000) + 1) AS name,
    FLOOR(RAND() * 100) + 1 AS age,
    CONCAT('Position', FLOOR(RAND() * 100000000) + 1) AS position
FROM
    INFORMATION_SCHEMA.COLUMNS as a
        CROSS JOIN
    INFORMATION_SCHEMA.COLUMNS as b
LIMIT 1000;
--建索引
create  index idx_nameagepos on User(name,age,position);
#具体查询
EXPLAIN select  id,name,age,position from User where name = 'User10052562' and age='38';
EXPLAIN select  id,name,age,position from User where  age='38' and position='Position57818398';
EXPLAIN select  id,name,age,position from User where  age='38';

2 相关分析，总是只看理论，记东西，时间真的会带走一切。