Answers for "alter table syntax in oracle"

alter table oracle

ALTER TABLE tablename MODIFY columnname varchar2(100)

update table syntax in oracle

{
    UPDATE table-Name [[AS] correlation-Name]
        SET column-Name = Value
        [ , column-Name = Value} ]*
        [WHERE clause] |
    UPDATE table-Name
        SET column-Name = Value
        [ , column-Name = Value ]*
        WHERE CURRENT OF
}