MySQL columns are of the text (or varchar) type and compared with numbers.

Today, I encountered a strange problem. One column in the MySQL table is of the text type, and the where condition in a row of query statements is:

Select * From tablename where columnname = 2;

The result is incorrect. We can find the result at in the record!

Double quotation marks (2) and the result is correct!

Puzzled! This is not found in the MySQL documentation. I found some comments on the Internet, as if MySQL encounters this column type and the given parameter value type does not match, it will convert the column in the MySQL record, that is to say, the value of a column is, converted to a number, and then converted to 2. Therefore, the conditions mentioned above will also find this record.

Reference: http://blog.chinaunix.net/uid-20690190-id-1894506.html