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If the type of the table field is varchar, but it stores pure numbers, how to sort them according to the size of the numbers?

The following methods are useful for both mysql and oracle

Order by field + 0

Order by field * 1

And so on can be realized.

Mysql > create table tn (id varchar (30), name varchar (50))

Mysql > show create table tn

+- -+

| | Table | Create Table |

+- -+

| | tn | CREATE TABLE `tn` (

`id` varchar (30) DEFAULT NULL

`name` varchar (50) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

Mysql > insert into tn values (1)

Query OK, 1 row affected (0.01sec)

Mysql > insert into tn values (10)

Query OK, 1 row affected (0.00 sec)

Mysql > insert into tn values (11)

Query OK, 1 row affected (0.00 sec)

Mysql > insert into tn values (2)

Query OK, 1 row affected (0.00 sec)

Mysql > insert into tn values (5)

Query OK, 1 row affected (0.00 sec)

Mysql > insert into tn values (3)

Query OK, 1 row affected (0.00 sec)

Mysql > insert into tn values (6)

Query OK, 1 row affected (0.00 sec)

Mysql > select * from tn

+-+ +

| | id | name |

+-+ +

| | 1 | a |

| | 10 | b |

| | 11 | bb |

| | 2 | bb |

| | 5 | c |

| | 3 | f | |

| | 6 | g |

+-+ +

Sort using order by statements

Mysql > select * from tn order by id desc

+-+ +

| | id | name |

+-+ +

| | 6 | g |

| | 5 | c |

| | 3 | f | |

| | 2 | bb |

| | 11 | bb |

| | 10 | b |

| | 1 | a |

+-+ +

7 rows in set (0.00 sec)

It doesn't seem to work, because the value of the id column is of type string.

Resolve:

Use field + 0 to solve

Mysql > select * from tn order by id+0 desc

+-+ +

| | id | name |

+-+ +

| | 11 | bb |

| | 10 | b |

| | 6 | g |

| | 5 | c |

| | 3 | f | |

| | 2 | bb |

| | 1 | a |

+-+ +

7 rows in set (0.00 sec)

Or use field * 1 to solve the problem

Mysql > select * from tn order by id*1 desc

+-+ +

| | id | name |

+-+ +

| | 11 | bb |

| | 10 | b |

| | 6 | g |

| | 5 | c |

| | 3 | f | |

| | 2 | bb |

| | 1 | a |

+-+ +

7 rows in set (0.00 sec)

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