This set entered on 5-12-2014
5.1.14.4
- p 318. KEYS. Filemaker knows what records are related because:
you tell it to expect them to have some data in common.
- An INVOICE has an INVOICE NUMBER that is very good at identifying the INVOICE because:
a. it is UNIQUE
b. It is UNCHANGING
c. It is CONSISTENT.
- In database terms, the INVOICE NUMBER is called:
a KEY
- A KEY is:
a FIELD whose value UNIQUELY, UNCHANGINGLY, and CONSISTENTLY identifies ONE RECORD.
- In database theory there are TWO TYPES of KEYS:
a. PRIMARY
b. FOREIGN
- How many TYPES of PRIMARY KEYS are there?
a. SURROGATE KEY
b. NATURAL KEY
- What is a SURROGATE KEY?
It is based on made up data, such as a number generated by the SERIAL NUMBER option. It never repeats, and has no meaning.
But UNLESS YOU GENERATE THE VALUE IN YOUR DATABASE, it is NOT A SURROGATE KEY, even if someone else made it up in THEIR SYSTEM.
A SURROGATE KEY IS MADE UP BY YOUR DATABASE.
- What is a NATURAL KEY?
It is a REAL PIECE of data that can be used as a KEY, such as an INTERNAL INVENTORY CONTROL NUMBER.
- Is a SOCIAL SECURITY NUMBER a NATURAL KEY?
YES. It may be a SURROGATE KEY to the Social Security Administration, BUT IT IS A NATURAL KEY TO YOU.
