SQL

alter table mysql

ALTER TABLE contacts
  ADD last_name varchar(40) NOT NULL
    AFTER contact_id,
  ADD first_name varchar(35) NULL
    AFTER last_name;

alter table query in mysql

ALTER TABLE `employees`CHANGE `emp_id` `emp_id` int(11) NULL;

my sql alter table

ALTER TABLE nom_table
MODIFY nom_colonne type_donnees

my sql alter table

ALTER TABLE nom_table
DROP nom_colonne