syntax for primary key code example
Example 1: what is primary key
Primary Key :
It is unique column in every table in a database
It can ONLY accept;
- nonduplicate values
- cannot be NULL
Foreign Key:
It is a column that comes from a different table and
using Foreign key tables are related each other
It is the primary key of another table
It can be duplicate or null for another table
Unique Key:
Only unique value and also can contain NULL
Example 2: what is primary key
PRIMARY KEY
Example 3: primary key sql
CREATE TABLE student
(
Roll integer (15) NOT NULL PRIMARY KEY,
Name varchar (255),
Class varchar (255),
Contact No varchar (255),
);