Difference between ALTER and UPDATE ALTER * It is a DDL. * It is used for adding, deleting and modifying attributes of the table. * Changes are made to the table structure. * By default, all the values in the tuple are initialized as null if the ALTER command is used. UPDATE * It is a DML. * It is used for updating the data in the existing table. * Changes are made to the data. * It sets the specified value to the tuple if update command is used.