SQL :Database Relationships

One to One Relationships

• In a one-to-one relationship, a key will appear only once in a related table.

One to Many and Many to One Relationships

• In a one-to-many relationship, keys from one table will appear multiple times in a related table.

Many to Many Relationships

• In some cases, you may need multiple instances on both sides of the relationship.

Self Referencing Relationships

• Customers can refer other customers to your shopping website.

Foreign Keys

• we always had these "****_id" fields that referenced a column in another table.

• Defining the Foreign Key Explicitly

Without Explicit Declaration

• Visualizing the Relationships in MySQL Workbench

• Detail

• shortcuts


• Non-identifying relationship
  A non-identifying relationship means that a child is related to parent but it can be identified by its own.
  
  

• Identifying relationship
  An identifying relationship means that the parent is needed to give identity to child. The child solely exists because of parent.