Question

I have a column with only one column ‘id’. The create statement of the table is:

CREATE TABLE `test` (
  `id` float default NULL
);

The value present in the table is:

id
-----
8.075

When I execute the query:

SELECT ROUND(id, 2) FROM test;

I am getting result ‘8.07’.
But when I simply execute the query:

SELECT ROUND(8.075,2);

I am getting value of ‘8.08’.

What can be done to get the consistent result in both the cases?

The demo of these query can be viewed here.

Answer 1

The result of a round depends on the implicit type of the literal 8.075.

The floating point number 8.075 is represented internally as the closest possible float, which is 8.07499999999999928946, which rounds to 2 places as 8.07.

If the literal 8.075 is being interpreted as a decimal, then the ’round-half-even’ rule is probably being applied. I’d look it up but MySQL’s website is down right now.