Hello world I'm talking about database normalization.

A Normalized database.

Will have these features.

In first normal form.

There are no repeating columns.

Create a separate table for each repetitive group.

After it's in first normal form.

Second normal form.

Says that there is no duplication of data.

If data appears in more than one row.

Put it in a separate table.

Use keys to relate to this data to the original table.

And in third normal form

All Fields must be dependent on the primary keys.

Remove ny fields that are not dependent on the keys.

We'll take a look at a case study.

Caryn Carter baby sets for several families.

She decides that setting up a database to keep track of her babysitting jobs would be a good idea.

She starts by writing down the type of information

That she has.

Here are three typical families: we have a mother,

And an address and a cell phone and an office phone for her.

And she has a daughter Jessica who's  2 years old.

Next we have a couple, Ben and Julie Beck. We have their address and we have phone numbers for Julie.

Add phone numbers for Ben.

They have two children.

And we have ages for those children.

Next we have Gloria Brown and a address.

Gloria is Raising her granddaughter, Crystal.

who is 7 years old.

We're going to look at some of these relationships and in particular ones where we have would have a potential.

Repeating columns. Each family resides at 1 address.

In this particular instance.

Each family has one or more adults

who arrange babysitting services.

Each adult has at least one phone number to contact them.

Each family has one or more children.

Or they wouldn't need a babysitter.  We can see the following relationships.

Each family or home has one or more adults.

And each adult.

Belongs to one and only one family.

Each family.

Has one to many children.

Each child belongs to one and only one.

family.

Adults

have one or more phone numbers.

Each phone number.

Belongs to one and only one adult.

We can't just put all that information.

Together. We're going to look at

how we break it up to avoid repeating columns.

Because of the relationships,

We're going to have tables with the following.

We're Going to have a table for family.

We're going to have another table for the adults, we're going to have a table of phone numbers, and we're going to have a

table for the children.

For the family.

There will be a family ID.

The address which consists of city, street, state, and zip code.

We're going to have a table adults and we'll need an adult ID.

The Family ID that they belong to.

Their given name.

And a family name.

Better not use first name and last name.

In many cultures the given name.

Comes last and the family name comes first.

For each adult

We have

The adult Id.

Phone number of the description such as cell, phone, fax.

And so on.

And each child has a Child ID.

Family ID.

Given name, family name, gender and birthday. We don't have the birth dates now.

But if we put in a field called age and we put in a 6 or somebody today,

That's going to become out of date at some point.

And we would have no way of knowing when that was put in there.

So if we at least have the year they were born we can figure out their current age.

And that's it.