数据库|mysql教程
数据
数据库-mysql教程
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1.功能需要
完成列表排序上移，下移，置顶功能！效果下图例：
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2设置思路
设置一个rank为之间戳，通过选择上移，就是将本记录与上一条记录rank值交换，下移就是将本条记录与下一条记录rank值交换，置顶就是将本记录与rank值最小的记录交换
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3.表数据结构
选择mysql记录上一条，下一条sql语句
SELECT * FROM user ORDER BY rank ASC
+----+------+---------+| ID | rank | name |+----+------+---------+| 1 | 1 | admin1 || 2 | 2 | admin2 || 3 | 3 | admin3 || 4 | 4 | admin4 || 5 | 5 | admin5 || 6 | 6 | admin6 || 7 | 7 | admin7 || 8 | 8 | admin8 || 9 | 9 | admin9 || 10 | 10 | admin10 || 11 | 11 | admin11 || 12 | 12 | admin12 |+----+------+---------+
4.选择上一行
select * from user where id <3 or id=(SELECT MIN(id) from user) order by id desc limit 1
+----+------+--------+| ID | rank | name |+----+------+--------+| 2 | 2 | admin2 |+----+------+--------+1 row in set (0.00 sec)
5.当id=1时
mysql> select * from user where id <1 or id=(SELECT MIN(id) from user) order by id desc limit 1;+----+------+--------+| ID | rank | name |+----+------+--------+| 1 | 1 | admin1 |+----+------+--------+1 row in set (0.00 sec)
6.选择下一行
mysql> select * from user where id > 3 OR ID=(SELECT MAX(ID) FROM user) ORDER BY id ASC LIMIT 1;+----+------+--------+| ID | rank | name |+----+------+--------+| 4 | 4 | admin4 |+----+------+--------+1 row in set (0.00 sec)
7.当id为最大值时
mysql> select * from user where id > 12 OR ID=(SELECT MAX(ID) FROM user) ORDER BY id ASC LIMIT 1;+----+------+---------+| ID | rank | name |+----+------+---------+| 12 | 12 | admin12 |+----+------+---------+1 row in set (0.00 sec)
