Suppose we query Clients Table by Date of Birth, and one of the returned results being a record having client id = CID1234.

Now if we query the same table for client id = CID1234 we should get the record with client id = CID1234 (maybe client id field is primary key or not, that does not matter). Nobody expects that this query to return no results found.

Edit : Trying to make it clear, lets say the returned record had a fieldX = XYZ, now querying on Table with the fieldX = XYZ should also include a record with client Id= CID1234 , if none of the returned records include such a record then it seems something is wrong.

Although this intuitively makes sense, my question is what is the name of this property and is it specific to SQL databases, or a whole category of Databases e.g. Non-SQL etc.

Is there a name for data systems that have such a property? Can this be found within Lambda calculus?

My original problem is SOA related, but knowing this a property in SQL databases made me ask it here, the original question is posted here : https://stackoverflow.com/questions/41215546/is-there-a-principal-that-requiers-total-of-possible-enumeration-results-to-add


If that value is unique and is used to identify a single row in a table ( in your example to uniquely identify a single client record) it would typically be considered a unique or primary key.

If it has some meaning and you already have a separate primary key it could could also be described as a business key or natural key.

Without a constraint to enforce uniqueness you cant guarantee the data is unique. You should be careful to avoid developing with that as an assumption.

  • I think I wasn't clear, the fact that record should be returned, it might as well be any other field, to make it clearer I add that it is not a primary key of the table. – Arjang Dec 19 '16 at 4:32
  • In SQL it should return exactly what you ask for. If it doesnt something is wrong or broken. In your other question you have an added layer of complexity which appears to have additional business logic or rules applied. – Sir Swears-a-lot Dec 19 '16 at 5:37
  • That is the question, what and why makes SQL behaviour to be as it is expected, I am trying to ascertain what makes SQL to behave according to those principles should also drive the API to be the same too, at least for the same Service-Operation. The question is what is name of the principle that makes SQL to behave as it does? is it something specified by lambda calculus? – Arjang Dec 19 '16 at 5:49

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