Wrong value returned from mysql float

问题

I have a table with high precision value, stored as Float. When I query the table for that value it returns rounded off value, rounded to 1st digit. But when I run the below query I am getting the value that I have stored,

SELECT MY_FLOAT_COL*1 FROM MY_TABLE;

What's going on inside Mysql?

回答1:

If you want to store exact values, you'd use the DECIMAL data types.

By manual of FLOAT:

The FLOAT and DOUBLE types represent approximate numeric data values. MySQL uses four bytes for single-precision values

The thing to mention here is approximation.

You can read more on floats here: http://dev.mysql.com/doc/internals/en/floating-point-types.html

来源：https://stackoverflow.com/questions/38997372/wrong-value-returned-from-mysql-float