Creation of primary key, foreign key, compound foreign key

--PRIMARY key
CREATE TABLE EMP (ID number constraint ID_PR primary key, name1 varchar (8));
CREATE TABLE EMP9 (ID number, name1 varchar (8), constraint ABA_PR primary key (ID,NAME1));
--FOREIGN key
CREATE TABLE EMP1 (ID number references emp (ID), name varchar (8));

--composite FOREIGN key
CREATE TABLE Emp0 (ID number, name varchar (8), Constraint fk_nam1e foreign key (id,name) references EMP9 (id,name1));

--PRIMARY key addition
CREATE TABLE EMP2 (ID number,name varchar (8), id1 number, constraint pk_id primary key (ID), Constraint fk_name foreign key (ID 1) references emp (ID))
The wording of--check constraint
CREATE TABLE Emp4 (ID number check (ID in (3)), name varchar (8));

Without a constraint name:

CREATE TABLE UserInfo (

ID Number (6) primary key,--primary key

Name VARCHAR2 () NOT null,--non-null

Sex number (1),

Age Number (3) default 18,

Birthday date,

Address VARCHAR2 (50),

Email varchar2 Unique,--only

Tel Number (11),

Deptno Number (2) References Dept (DEPTNO)-FOREIGN key

);

Creation of primary key, foreign key, compound foreign key