mysql 练习笔记

从一个数据表中找出连续n条满足条件的记录

例子demo 从数据表中找出连续三条或者三次以上分数超过80分的记录

MariaDB [testdatabase]> select * from class;
+----+-----------+---------+-------+
| id | classname | teacher | grade |
+----+-----------+---------+-------+
|   |        | peter   |     |
|   |        | john    |     |
|   |        | tom     |     |
|   |        | mango   |     |
|   |        | peter   |     |
|   |        | peter   |     |
|   |        | haden   |     |
|   |        | james   |     |
|   |        | jakie   |     |
|   |        | tom     |     |
|  |        | mango   |     |
|  |        | jula    |     |
|  |        | john    |     |
+----+-----------+---------+-------+
SQL语句如下

select * from class where id in (
　　select DISTINCT n1.id from class n1,class n2,class n3 where 
　　　　　(n1.grade>80 and n2.grade>80 and n3.grade>80 and 
　　　　　((n1.id + 1= n2.id and n2.id +1 = n3.id) OR 
　　　　　　(n1.id-1=n2.id and n1.id+1=n3.id) OR 
　　　　　　(n1.id-1=n2.id and n1.id-2=n3.id) ) 
　　　　　) order by n1.id )

输出结果

+----+-----------+---------+-------+
| id | classname | teacher | grade |
+----+-----------+---------+-------+
|  0 | 101       | peter   |    85 |
|  1 | 102       | john    |    86 |
|  2 | 103       | tom     |    87 |
|  3 | 104       | mango   |    88 |
+----+-----------+---------+-------+