Why are My MySQL Floating-Point Comparisons Inaccurate?

MySQL Floating Point Comparison Issues

You're encountering problems with floating-point comparisons in MySQL because floating-point numbers are inherently inaccurate due to the way they are represented in binary. This can lead to unexpected results when comparing values that should be equal.

Consider the following example:

SELECT COUNT(*) FROM `users` WHERE `points` > "12.75"

You would expect this query to return 2, since there are two rows with points greater than 12.75. However, it returns 3 because floating-point numbers are represented with a limited number of bits, which leads to rounding errors.

Experts recommend using the DECIMAL data type instead of FLOAT or DOUBLE for financial calculations and other applications where precision is crucial. DECIMAL stores values as fixed-point numbers, eliminating the rounding errors that can occur with floating-point numbers.

To illustrate, let's convert the points column from FLOAT to DECIMAL:

ALTER TABLE `users` MODIFY COLUMN `points` DECIMAL(6,2)

Now, when you run the query again, you will get the expected result of 2.

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