We also couldnвЂ™t have many columns for class ID values, as this would get messy and create a limit on the number of relationships. This would mean we have one column for storing multiple values, which is very hard for maintenance and querying. We canвЂ™t add the primary key of one table into the other, or both, because this only stores a single relationship, and we need many. This means a student has many classes, and a class has many students. A class can have many students (for example, there may be 20 students in one class).A student can be enrolled in multiple classes at a time (for example, they may have three or four classes per semester).We capture details about students who attend classes, among other things. LetвЂ™s say we are creating a database for a university (which is an example IвЂ™ve used often). However, for many-to-many relationships, itвЂ™s a bit different.

Handling a one-to-one relationship or a one-or-many relationship can be done by adding the primary key of one table into the other table as a foreign key. Many-to-many: Multiple records in one table are related to multiple records in another table.One-to-many: A record in one table is related to many records in another table.One-to-one: A record in one table is related to one record in another table.There are three ways in which a table can be related to another table: When normalizing a database or adding tables to an existing database, we need to be able to relate tables to each other.

Relating databases in idatabase