Strange behaviour of the float type

Question

I have the following table:

+------------+--------+------+-----+---------+----------------+
| Field      | Type   | Null | Key | Default | Extra          |
+------------+--------+------+-----+---------+----------------+
| id         | double | NO   | PRI | NULL    | auto_increment |
| az1        | float  | YES  |     | 989898  |                |
| el1        | float  | YES  |     | 989898  |                |
| az2        | float  | YES  |     | 989898  |                |
| el2        | float  | YES  |     | 989898  |                |
| rfs_angle  | float  | YES  |     | 989898  |                |
| scan_speed | float  | YES  |     | 989898  |                |
+------------+--------+------+-----+---------+----------------+

I inserted this data more than 100times

INSERT INTO lidar_traj_table (az1, el1, az2, el2, rfs_angle, scan_speed)  VALUES (49.100, 0.000,989898,8.000,1.0,1.000)

When I'm trying to select the data I'm receiving nothing:

SELECT * FROM lidar_traj_table WHERE az1=49.1

When I'm selecting smaller data then 49.1 than I get all the rows

SELECT * FROM lidar_traj_table WHERE az1<=49.1

Why am I getting empty result for this:

SELECT * FROM lidar_traj_table WHERE az1=49.1

Answer 1

If you want to store exact values then you should use the DECIMAL data type instead of FLOAT.