1. The document discusses various SQL constraints that can be used when creating tables such as PRIMARY KEY, NOT NULL, DEFAULT, UNIQUE, and AUTO_INCREMENT. 2. Examples are provided of creating tables with different constraints like PRIMARY KEY to enforce a unique identifier column, NOT NULL for required fields, DEFAULT to set a default value, and UNIQUE for uniquely identifying columns. 3. The document also covers composite UNIQUE constraints to enforce uniqueness across multiple columns together rather than individually.

1. 데이터베이스개론CREATE TABLE, 제약조건
NHN NEXT 정호영
나눔고딕및나눔고딕코딩글꼴을설치해주세요.

2. 이번에배울내용
1.CREATE
2.간단한데이터타입
3.몇가지제약조건

3. 복습:사용자추가/데이터베이스추가
m> CREATE USER 'popi'@'localhost' IDENTIFIED BY 'db1004';
m> CREATE DATABASE popidb;
m> GRANT ALL ON popidb.* TO 'popi'@'localhost' WITH GRANT OPTION;
m> flush privileges;
m> quit;
$ mysql-u popi-p
m> show databases;
m> use popidb;

4. 복습:간단CRUD예제
m> USE popidb;
m> CREATE TABLE student(
namechar(16),
id char(16)
birth date,
gpadouble
);
m> INSERT INTO student values('Hoyoung', 'honux', '1995-12-9', 3.5),
('gildong', 'hong', '1500-3-1', 0.9);
m> select * from student;

5. CREATETABLE:테이블을만드는명령
CREATE TABLE 테이블이름(
컬럼1데이터타입1, 컬럼2 데이터타입2, …
제약조건1, 제약조건2, ... );

6. 테이블정보보기
M> DESC student;
M> SHOW CREATE TABLE student;

7. 간단한데이터타입
-용도에따라적절한데이터타입을선택하자.
타입
설명
INT
정수
DEC(5, 2)
정수3자리
소수점2자리
DOUBLE
실수
CHAR(8)
고정크기문자열
VARCHAR(16)
가변문자열

8. 옥션의사용자정보를저장하는테이블을만들어봅시다.
Q1.같은값이두개들어갔는데괜찮을까요?
Q2.반드시고유한값을가져야하는컬럼이있을까요?
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24),
birth date,
last datetime,
money dec(8, 2)
);
m> INSERT INTO auction_user(id, money) VALUES ('k5', 100), ('k5', 100);
m> SELECT * FROM auction_user;

9. PrimaryKey제약조건
고유해야만하는값중에서대표값하나를기본키로지정
일반적으로테이블은하나의PrimaryKey를가집니다.
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24),
birth date,
last datetime,
money dec(8, 2),
PRIMARY KEY(id)
);
m> INSERT INTO auction_user(id, money) VALUES ('k5', 100);
m> INSERT INTO auction_user(id, money) VALUES ('k5', 100);

10. 데이터를삽입합니다.
다시데이터를살펴봅시다.
이대로괜찮을까요?
m> INSERT INTO auction_user(id, money) VALUES ('ho', 99.99);

11. NOTNULL
반드시있어야할값의일부가NULL이되었습니다.
반드시값이필요한컬럼에는NOTNULL을사용합니다.
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24) NOT NULL,
birth date,
last datetime,
money dec(8, 2),
PRIMARY KEY(id)
);
m> INSERT INTO auction_user(id, money) VALUES ('happy', 100);
m> INSERT INTO auction_user(id, name, money) VALUES ('happy', 'kim', 100);

12. 테이블속성을다시봅시다.

13. DEFAULT
money는NOTNULL이고최초생성시에$5를준다고합니다.
이럴때DEAULT키워드를사용할수있습니다.
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24) NOT NULL,
birth date,
last datetime,
money dec(8, 2) NOT NULL DEFAULT 5.00,
PRIMARY KEY(id)
);
m> INSERT INTO auction_user(id, name) VALUES ('nero', 'ko');
m> SELECT * FROM auction_user;

14. UNIQUE
기본키외에고유한값을가지는컬럼에UNIQUE를사용합니다.
이제이름이같은유저두명이존재할수없습니다.
잘못설계했습니다…
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24) NOT NULL UNIQUE,
birth date,
last datetime,
money dec(8, 2) NOT NULL DEFAULT 5.00,
PRIMARY KEY(id)
);

15. 생일말고주민번호를추가로저장하기로했습니다.
괜찮을까요?
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24) NOT NULL,
ssn1 char(6),
ssn2 char(7),
last datetime,
money dec(8, 2) NOT NULL DEFAULT 5.00,
PRIMARY KEY(id)
);

16. 생일말고주민번호를추가로저장하기로했습니다.
괜찮을까요?
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24) NOT NULL,
ssn1 char(6) UNIQUE,
ssn2 char(7) UNIQUE,
last datetime,
money dec(8, 2) NOT NULL DEFAULT 5.00,
PRIMARY KEY(id)
);

17. 생일말고주민번호를추가로저장하기로했습니다.
이제괜찮습니다.
m> DROP TABLE IF EXISTS auction_user;
m> CREATE TABLE auction_user(
id varchar(16),
name varchar(24) NOT NULL,
ssn1 char(6),
ssn2 char(7),
last datetime,
money dec(8, 2) NOT NULL DEFAULT 5.00,
PRIMARY KEY(id),
UNIQUE(ssn1, ssn2)
);

18. MySQL만의제약조건으
로PRIMARYKEYAUTO_INCREMENT가있습니다.
m> CREATE TABLE inc_test(
numintPRIMARY KEY AUTO_INCREMENT,
value char(8)
);
m> INSERT INTO inc_test(value) VALUES ('a'), ('b'), ('c');
m> SELECT * FROM inc_test;

19. THANK YOU!!!