Entity Relationship Diagram (ERD)

A database term.

Before you design a database, it is a good idea to sketch out what the various things within the database are meant to be doing. What is the 'concept' behind the database i.e. what is its purpose.

An entity relationship diagram is an useful planning tool for doing this.

An 'entity' can be anything you want it to be.

For example, imagine you are designing a stock control database. One entity might be the "stock", another entity might be "customer". So an ERD would be used to describe the actions that can take place between these two entities such as 'Can Order' or 'Buys' etc.

An 'entity' in a database often ends up as a single table having a number of records, each of which have a number of fields.

So two simple entities may end up as two tables. Of course a complex database may have thousands of tables with hundreds of relationships.

2020-10