What does MySQL converting varchar to char? -

when add new table, made mistake : field varchar(255), have write join queries. alter table make char(6).

my question : mysql in case ? trims right ?

rather worry mysql or doesn't why not convert data before change.

e.g.

update yourtable set yourfield = left(yourfield,6);  alter table yourtable modify column yourfield char(6) 

you should note if column data long won't let alter assuming enable strict sql mode see shef's complete answer