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    Primary Key
                     Primary key is a field which is used to uniquely identify records in a database. It is a unique field

                     and it cannot be left blank. There can be only one primary key in a table.
                     In the Student Table, Student_ID is the primary key, which is used to uniquely identify the records.

                     Foreign Key

                     A foreign key is a field in one table that refers to the primary key in another table. It helps to
                     establish a relationship between two tables. A foreign key makes sure that data in one table
                     matches data in another table.

                     Let’s understand the relationship among tables in a relational database with the help of an example.
                                                                Student Table

                         Student_      First_       Last_        Date of                  Email            Course_
                             ID        Name        Name           Birth                                       ID

                              1      Aarav        Sharma      15-Mar-2012     aarav.sharma@gmail.com          C101
                              2      Priya        Patel       20-May-2012     priya.patel@gmail.com           C102
                              3      Rahul        Verma       10-Mar-2012     rahul.verma@gmail.com           C103
                              4      Sneha        Iyer        25-Nov-2011     sneha.iyer@gmail.com            C101

                             5       Dev          Kapoor      12-Jul-2012     dev.kapoor@gmail.com            C102

                                                                Course Table

                                Course_ID                        Course Name                     Teacher_Name

                                   C101                Mathematics                       Dr. Ramesh Kumar

                                   C102                Science                           Ms. Priya Sethi
                                   C103                Social Studies                    Mr. Rahul Sharma

                     In this example, the Student Table and Course Table share a common field named Course_ID.
                     The Course_ID in the Student Table is a foreign key that references the Course_ID (a primary key)
                     in the Course Table.

                     From this relationship, the following information gets extracted:

                       One Course (Course Table) is opted by many Students (Student Table).
                       Each student (Student Table) is linked to only one course via Course_ID (Foreign Key).

                          Tick ( ) if you know this.

                          ▶  Data backup in databases means making a copy of the database files.
                          ▶  A record is a collection of related data stored in different fields.

                                                                                              MySQL: My First Database  59

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