MySQL基础面试题

create table `t1` (
`id` double ,
`name` varchar (300),
`score` double
);
insert into `t1` (`id`, `name`, `score`) values('1','n1','59');
insert into `t1` (`id`, `name`, `score`) values('2','n2','66');
insert into `t1` (`id`, `name`, `score`) values('3','n3','78');
insert into `t1` (`id`, `name`, `score`) values('4','n1','48');
insert into `t1` (`id`, `name`, `score`) values('5','n3','85');
insert into `t1` (`id`, `name`, `score`) values('6','n5','51');
insert into `t1` (`id`, `name`, `score`) values('7','n4','98');
insert into `t1` (`id`, `name`, `score`) values('8','n5','53');
insert into `t1` (`id`, `name`, `score`) values('9','n2','67');
insert into `t1` (`id`, `name`, `score`) values('10','n4','88');
1. 单分数最高的人和单分数最低的人。
mysql> select name,max(score) from t1;
2. 两门分数加起来的第2至5名。
mysql> select name,sum(score) from t1 group by name order by sum(score) desc limit 1,4;
SELECT a.name,SUM(a.score) FROM t1 as a GROUP BY a.name ORDER BY a.score DESC LIMIT 1,4;+------+------------+
| name | sum(score) |
+------+------------+
| n3   |        163 |
| n2   |        133 |
| n1   |        107 |
| n5   |        104 |
+------+------------+
3. 两门总分数在150分以下的人。
select name sum(score) from t1 group by name having sum(score) < 150;
SELECT a.name,SUM(a.score) FROM t1 as a  GROUP BY a.name HAVING SUM(a.score)<150 ORDER BY SUM(a.score) DESC;
4. 两门平均分数介于60和80的人。
select name,avg(score) from t1 group by name having avg(score) between 60 and 80;
select name,avg(score) from t1 group by name having ave(score) >60 and avg(score) <80;
SELECT a.name,AVG(a.score) FROM t1 as a  GROUP BY a.name HAVING   AVG(a.score)BETWEEN 60 AND 80 ORDER BY AVG(a.score) DESC;
5. 总分大于150分，平均分小于90分的人数。
mysql> select name,sum(score),avg(score) from t1 group by name having sum(score)>150 and avg(score)<90;
SELECT a.name,AVG(a.score),SUM(a.score)  FROM t1 as a  GROUP BY a.name HAVING   AVG(a.score)<90  AND SUM(a.score)>150  ORDER BY AVG(a.score) DESC;
+------+------------+------------+
| name | sum(score) | avg(score) |
+------+------------+------------+
| n3   |    163   |     81.5 |
+------+------------+------------+
1 row in set (0.00 sec)
6. 总分大于150分，平均分小于90分的人数有几个。
select count(distinct name) from t1 group by name having sum(score) > 150 and avg(score) < 90;
SELECT a.name,AVG(a.score),SUM(a.score),COUNT(distinct  a.name)  FROM t1 as a  GROUP BY a.name HAVING   AVG(a.score)<90  AND SUM(a.score)>150  ORDER BY AVG(a.score) DESC;