MySQL Bugs: #16037: Why isn't (1.11 * 10) equal to 11.10?

Bug #16037	Why isn't (1.11 * 10) equal to 11.10?
Submitted:	28 Dec 2005 10:35	Modified:	28 Dec 2005 14:03
Reporter:	Ola Oke	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Server	Severity:	S2 (Serious)
Version:	4.1.10a-nt	OS:	Windows (Windows 2000)
Assigned to:		CPU Architecture:	Any

Description:
Is this due to a MYSQL bug?  Please read on:

I am using version: 4.1.10a-nt on Windows 2000

Can anyone please tell me why (1.11 * 10) is not equal to 11.10, in the query below. I expect the two to be equal because (1.11 * 10) is the same as 11.10, yet the query always brings back 0 which means false.

This is the query that does not bring back the expected result:
SELECT (1.11 * 10), (1.11 * 10) = 11.10
FROM dual

This query does bring back the expected result (Why is this correct whereas the first query - above - is not?):
SELECT (1.11 * 1), (1.11 * 1) = 1.11
FROM dual

Depending on your db vertion you may already have the dual table, therefore, please test these queries on your db for verification.

Note:  The answer to this puzzle will enable me to deal with a bug in our application.

Thank you.

Ola.

How to repeat:
To reproduce the 'bug', run this query:

This is the query that does not bring back the expected result:
SELECT (1.11 * 10), (1.11 * 10) = 11.10
FROM dual

(1.11 * 10) = 11.10 will bring back a value of 0 instead of 1

Thank you for a problem report. It is a well-known and documented feature (limitation) of all version up to 5.0.3. Please, read http://dev.mysql.com/doc/refman/5.0/en/precision-math-examples.html, for example.

Noted.  Thanks.