(데이터베이스) 다중 테이블 연산

같은 결과를 내는 여러가지 방법.

1.
CREATE TABLE profession
(
 id INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
 profession varchar(20)
);
 INSERT INTO profession(profession)
  SELECT profession FROM my_contacts
  GROUP BY profession
  ORDER BY profession

2.
  CREATE TABLE profession AS
   SELECT profession FROM my_contacts
   GROUP BY profession
   ORDER BY profession
ALTER TABLE profession
ADD COLUMN id INT NOT NULL AUTO_INCREMENT FIRST,
ADD PRIMARY KEY(id);

3. CREATE TABLE profession
(
 id INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
 profession varchar(20)
)AS
 SELECT profession FROM my_contacts
 GROUP BY profession
 ORDER BY profession