code: public function dropColumn($table, $column)
      {
          return 'ALTER TABLE ' . $this->db->quoteTableName($table)
              . ' DROP COLUMN ' . $this->db->quoteColumnName($column);
      }
docs: Builds a SQL statement for dropping a DB column.
  @param string $table the table whose column is to be dropped. The name will be properly quoted by the method.
  @param string $column the name of the column to be dropped. The name will be properly quoted by the method.
  @return string the SQL statement for dropping a DB column.