mysql 条件 'equal' 显示条件 'like' 属性

Question

select * from order_info where order_id = 48;

The mysql command show above is a very simple sentence, but the result below seems not to meet my expectation, it is more similar to like condition. retrieval result

I don't know if the type of field may affect the result as the field 'order_id' is varchar type. When I change the condition to " where order_id = '48' ", It meets my expectation.

Can anyone tell me why is this case? Why conditon 'equal' show unexpected outcomes?

I expect the result should be empty as the table does not have the record whose order_id is equal to 48.

Answer 1

Consider this -

SELECT CAST('48KKKK' AS INT);

You might expect it to fail, it doesn't and the result is 48. Your query is implicitly converting order id before comparison because you are comparing to an integer so the result of your query is correct and it's a gotcha to remember..