You've got your good things, and you've got mine.
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- Today, 17:37
- May 21, 2018
That may be fine, not to have any relationships established. Having relationships established in your relationship window is not always required. It is also not the same as joins in a query. You do not need to build a relationship just to do a simple join.i dont have no relationship inside. ok have some query with relationship but this is not what i see on other databases.
You need a relationship to ensure referential integrity. And you do not always do you need it or even want it. You need it when you have child records that would not make sense to be in the database without a parent record. For example if you had a database that tracks your suppliers and their products. You would not want to add a product to your database if you did not have a supplier to order it from. You have to add the supplier first then you are required to assign a new product to a supplier. So if you enforce referential integrity you cannot do the following
1) Add a product without a foreign key related to a supplier. You cannot leave it blank and cannot assign an incorrect key
2) Cannot delete the supplier with out deleting the children first
This will ensure you never get orphans in your database. That would be a product not related to a supplier
3) If you choose allow cascade deletes it will allow you to delete a parent that has children. It will prompt you that there are X child records and they will be deleted. This overrides number 2 above.
4) Not used as much since most peope use an autonumber for a primary key. But assume you made your own primary key and the key for your supplier "ACME Industries" is AI. All the child records would be related by AI. If you change the Primary key to ACME, the related children foreign keys will change from AI to ACME keeping the relationship
If you create a relationship in the relationship window it creates defaults. So when you create a query it will automatically create a join. However you can edit or delete this join in the query window. If a relationship was not created prior you can still make a join on your own.