• Add new values (we've seen this!)

  INSERT INTO abductee(fname, lname, zipcode, numTrips)  VALUES ('Mickey','Mouse','99999',3);
                       

• Change but don't delete values that are already there. (Fix up table!)

  UPDATE abductee     SET addressline='Disney World',zipcode='37383'     WHERE lname='Mouse';
                       

• Remove ROWS from a table. (Fix up table!)

  DELETE FROM abductee     WHERE lname='Mouse';

In the below, columns added to an existing table with existing data will have NULL stored as their value for the existing rows.

• ALTER TABLE tablename
        ADD COLUMN columnname columntype
        [FIRST | AFTER columnname ];
  

• ALTER TABLE tablename
        DROP COLUMN columnname;
  

• ALTER TABLE tablename
        CHANGE COLUMN columnname newcolumnname newcolumntype;
  

• ALTER TABLE oldtablename
        RENAME AS newtablename;