How do I change the datatype of an field in a table. Table previously got
added the wrong datatyp.

ALTER TABLE MineTable
ADD CityGMT INTEGER NOT NULL';

Now I want CityGMT to become an float so i tried :

ALTER TABLE CItyGMT
ALTER CityGMT FLOAT NOT NULL;

ALTER TABLE CityGMT
MODIFY CityGMT FLOAT NOT NULL;

Both failed what would be the right syntax.