Add Delete primary key in Oracle

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1. Create a PRIMARY KEY constraint while creating a table
(1) No naming
CREATE TABLE Student (
StudentID int PRIMARY key NOT NULL,
Studentname varchar (8),
age int);
(2) have a name
CREATE TABLE Students (
StudentID int,
Studentname varchar (8),
Age int,
Constraint yy primary KEY (StudentID));

2. Delete the existing PRIMARY KEY constraint in the table
(1) No naming
Available as SELECT * from User_cons_columns;
Find primary key name in table student table with primary key named sys_c002715
ALTER TABLE student drop constraint sys_c002715;
(2) have a name
ALTER TABLE students drop constraint yy;

3. Add a PRIMARY KEY constraint to the table
ALTER TABLE student ADD constraint Pk_student primary key (StudentID);

Add Delete primary key in Oracle