在 MySQL 中，是否可以按升序和降序划分记录并交替显示它们?
mysqlmysqli database
是的，您可以在 MySQL 中通过首先获取中间值来执行此操作。让我们首先创建一个表:
mysql> create table DemoTable ( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY ); Query OK, 0 rows affected (0.65 sec)
下面是使用 insert 命令在表中插入一些记录的查询:
mysql> insert into DemoTable values(); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.10 sec)
以下是使用 select 命令显示表中记录的查询:
mysql> select *from DemoTable;
这将产生以下输出 −
+--------+ | UserId | +--------+ | 1 | | 2 | | 3 | | 4 | | 5 | | 6 | | 7 | | 8 | | 9 | | 10 | +--------+ 10 rows in set (0.00 sec)
以下是先获取中间值的查询:
mysql> set @middleValue=(select max(UserId) from DemoTable)/2; Query OK, 0 rows affected (0.01 sec)
现在，让我们交替获取升序和降序值:
mysql> select *from DemoTable ORDER BY (IF(UserId <@middleValue,@middleValue*2- UserId,UserId-1)) DESC,UserId ASC;
这将产生以下输出 −
+--------+ | UserId | +--------+ | 1 | | 10| | 2 | | 9 | | 3 | | 8 | | 4 | | 7 | | 6 | | 5 | +--------+ 10 rows in set (0.00 sec)
