Key fields are individual pieces of data that are unique (only appear once).
Key fields are used to differentiate one record from another.
In our patient's database, the key field is the Patient Id. Every patient has a different Id Number. We can identify each patient uniquely and correctly. Imagine if the doctor mixed two patients up and gave them the wrong medicine!!
Why is Patient Id suitable for the Key Field? Only the Patient Id is suitable for use as the unique key field. Remember the key field MUSTcontain only data thatCAN NEVER REPEAT. Look at the table below and think about it:
linking tables: relationships
What is a relationship?
A relationship is formed when our two tables are joined together.
Relationships make use of key fields and primary keys to allow
the two tables to communicate with each other and share their data.
Once the tables are linked together each one can read data from the other.
How do you form the relationship? (link the tables)
In order to link the tables we need to use a common field.
A common field is data that appears in BOTH tables.
No comments:
Post a Comment