I am looking for help with database design for a small project I am working on.

In short what I am trying to achieve is to have say the following tables:

Paddocks

• Paddock ID
• Paddock Name
• Paddock Size
• etc.

Cattle

• Herd ID
• Herd Name
• Number of cows
• Current Paddock

Cattle_Movements

• Herd Name
• Current Paddock
• New Paddock
• Date
• etc.

I was hoping to have the 'Cattle_Movements' table be like a summary of all movements of a herd of cattle. And when a herd is moved from one paddock to another it would update the 'Current Paddock' field in the 'Cattle' table.

At this stage I am trying to workout the relationships, queries and high level process that I will need to implement.

Any help will be greatly appreciated.

CodePudding user response：

Start by setting up a normalized table structure. make the tables below and hook them together with the relationships tool on the ribbon under database tools-relationships. To create a relationship drag the primary key from one table to the corresponding and same named foreign key in the table that will be the many side of the relationship. In the pop up make sure to check the enforce referential integrity, cascade update, and cascade delete checkboxes.

I've highlighted the two "Many to Many Relationships" in this normalization. HerdsPaddocks is a more generic name for the CattleMovements Table. There are other possible normalized table structures, but the subtle differences are beyond the scope of this answer. When you are ready, look up table normalization and Many to Many Relationships.

Next, Close the Relationships tool, select a table from the sidebar and on the ribbon under Create hit create form. Do this for all the tables. Now we have a working database but you need to learn how to use it. So play!

Below I gave some play suggestions, but just play with everything until you figure out how to use the forms to (add, search, edit) cows, herds, and paddocks. Also learn why you should delete the primary keys from all the forms and how to replace the foreign keys like CattleType in the Cattle Table with the user friendly CattleTypeDesscription from the CattleTypes Table.

Start with the Herds table and enter some random herds. (pro tip: never add data to the table directly except when playing the error rate is too high). Then Open the herds form where you can browse and edit the herds.
Play tips: In the Table Herds HerdID is both an autonumber and a primary key. It behaves differently from the other columns. Check it out. after that delete the HerdID textbox from the form and see what happens(a good thing). How do you add herds using the Herds Form? Moving on to playing with the Cattle form, first make sure to add a few CattleTypes to the CattleTypes table. Then at some point, try replacing the CattleTypeID in the Cattle Form with the CattleTypeDescription:

'Query 3 SQL from SQL pane of query designer
SELECT Count(Cattle.CowName) AS CountOfCowName
FROM Paddocks INNER JOIN ((Herds INNER JOIN (Cattle INNER JOIN CattleHerds ON Cattle.CattleID = CattleHerds.CattleID) ON Herds.HerdID = CattleHerds.HerdID) INNER JOIN HerdsPaddocks ON Herds.HerdID = HerdsPaddocks.HerdID) ON Paddocks.PaddockID = HerdsPaddocks.PaddockID
GROUP BY Herds.HerdName, Paddocks.PaddockName, HerdsPaddocks.HerdPaddockEndDate, HerdsPaddocks.HerdPaddockStartDate
HAVING (((Paddocks.PaddockName)="holds10cattle") AND ((HerdsPaddocks.HerdPaddockEndDate) Is Null) AND ((HerdsPaddocks.HerdPaddockStartDate)<Now()))
ORDER BY HerdsPaddocks.HerdPaddockStartDate;