MySql: Compare 2 strings which are numbers?

问题

I have a column in my table, it holds values such as 100012345. The column is varchar. Now I want to compare this to similiar values in a where:

... where myColumn > '100012345'

for example. How could I do that?

Thanks!

回答1:

select * from your_table
where cast(your_column as signed) = 100012345

回答2:

Have you tried to do it normally, like this:

... where myColumn > 100012345

That should work!, mysql automatically casts a string to number when it's in the context of a number operation. In the same way it casts a number to string if it's used in a string context. See the examples in the type conversion docs:

To cast a string to a numeric value in numeric context, you normally do not have to do anything other than to use the string value as though it were a number:

mysql> SELECT 1+'1';
       -> 2

If you use a string in an arithmetic operation, it is converted to a floating-point number during expression evaluation.

If you use a number in string context, the number automatically is converted to a string:

mysql> SELECT CONCAT('hello you ',2);
        -> 'hello you 2'

回答3:

You don't have to cast strings into integers to compare, mysql does it automatically.

http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html

回答4:

You can cast the value to an integer:

CAST(myColumn AS INTEGER)

来源：https://stackoverflow.com/questions/12749219/mysql-compare-2-strings-which-are-numbers