ALTER MODIFY change everything to 0

[Thomas Kwan]

I had a column originally defined as FLOAT. I found out
later on that the default FLOAT only accept 2 decimals.
So I issued

ALTER table <TABLE> modify price FLOAT(8,4);

After the ALTER execution, everything is turned into 0.0.
I wonder if this is the right thing to do. If not, do you
have pointers on how to change the schema from
FLOAT to FLOAT(8,4)

My mysql version is  3.22.30

thanks
thomas