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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_ID  First_Name      Last_Name      Date of Birth            Email              Course_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).

                       RAPID RECALL                             Tick ( ) if you know this.

                          1.  Data backup in databases means making a copy of the database files.

                          2.  A record is a collection of related data stored in different fields.

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