Unusual MySQL behavior on UPDATE?

Question

MySQL

Good day.
There is a table with a FLOAT type column (it stores the state of a certain virtual account).
Write-off is made by the following request:

UPDATE client_data SET `client_balance` = (`client_balance` - %сумма%) WHERE `id` = %id клиента%

But it works as follows:
1) It was 1.5, 1 was written off - 0.5 remained (as it should be)
2) It was 1.1, 1 was written off - 0.1 remained (as it should be)
3) It was 1.1, 1.1 was written off - left ( attention) 2.38419E-8 !
Actually, such behavior is not clear. Why is that?

Answer 1

Read here: dev.mysql.com/doc/refman/5.0/en/problems-with-float.html
Floats store approximate values. Use decimal

Answer 2

I advise you to read this: dev.mysql.com/doc/refman/5.1/en/problems-with-float.html
This behavior is due to the peculiarity of storing real numbers. And this applies to almost all programming languages.
It is really better to use the DECIMAL type to store the balance.

Answer 3

Because it's a float.
Round or use decimal.

Answer 4

faced the same problem. changing float type to decimal helps