Hi, on my database I have a customer table and a pet table.
One customer can have more than one pet
One to many relationship. I did set a referential integrity so on my database I can not have a pet without a customer.
But what I actually would like to know is how can I avoid duplicate customers
for example I can have many surnames SMITH and I can have many postcodes TW14 8EE, however I can have only ONE customer SMITH in TW14 8EE, how can I setup so the system does not accept another SMITH in TW14 8EE. Thank you

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Reply from Alex Hedley:

There could be two Smiths in the same postcode so it might be worth thinking about your requirements.
Expert 23 explains about stopping duplicates.