MySQL中ORDER BY columnname * 1的用途是什么？
MySQL会将列隐式转换为数字。以下是语法-
select * from yourTableName order by yourColumnName*1;
让我们首先创建一个-
mysql> create table DemoTable1441 -> ( -> Id varchar(30) -> );
使用insert在表中插入一些记录-
mysql> insert into DemoTable1441 values('301');
mysql> insert into DemoTable1441 values('23');
mysql> insert into DemoTable1441 values('345');
mysql> insert into DemoTable1441 values('10');
mysql> insert into DemoTable1441 values('38');使用选择显示表中的所有记录-
mysql> select * from DemoTable1441;
这将产生以下输出-
+------+ | Id | +------+ | 301 | | 23 | | 345 | | 10 | | 38 | +------+ 5 rows in set (0.00 sec)
以下是按列名*1使用订单的查询-
mysql> select * from DemoTable1441 -> order by id*1;
这将产生以下输出-
+------+ | Id | +------+ | 10 | | 23 | | 38 | | 301 | | 345 | +------+ 5 rows in set (0.00 sec)