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Consider a mobile store application designed for the customers to buy mobiles of their choice. The store has various models of mobiles. Every mobile is identified with a unique mobileid. Every model has a different batterylife and cost.

Here is a relational schema which represents this application:

mobile (mobileid, model, cost, batterylife)

The functional dependencies are given below:

mobileid -> model

model -> cost, batterylife

The database designers are required to identify the type of dependency/ dependencies existing in each of the given ones. Can you help with the identification of dependencies?

So we can say that transitive dependency exists (mobileid -> cost , batterylife).But my question is , is there is only one dependency (transitive) or can I say mobile -> model and model -> cost , batterylife both are fully functional dependencies , so that there are 3 dependencies going on in given relational schema .

philipxy
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Gayatri Barhate
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  • Where are you stuck quoting & applying a definition of what it means for a FD to hold? What did your research about determining what FDs hold show? https://stackoverflow.com/a/42945522/3404097 https://stackoverflow.com/a/42269533/3404097 – philipxy Apr 21 '21 at 07:02
  • Your "I have these FDs" doesn't make sense. "These are all the FDs that hold"?--Not possible. "These are all the non-trivial FDs that hold"?--Not possible. "These are some FDs that hold"?--Question can't be answered. Find out what a *cover* is & what the exact conditions are to apply a particular definition/rule/algorithm. To determine CKs & NFs we must be given FDs that form a cover. Sometimes a minimal/irreducible cover. And the set of all attributes must be given. [See this answer.](https://stackoverflow.com/a/53386492/3404097) – philipxy Apr 21 '21 at 09:54
  • Does this answer your question? [Identifying transitive dependencies](https://stackoverflow.com/questions/27393366/identifying-transitive-dependencies) – philipxy Apr 21 '21 at 10:26
  • @philipxy Yes I got it ! – Gayatri Barhate Apr 23 '21 at 04:22
  • You can click to agree about a duplicate or click on your own suggestion for a duplicate. But also always edit your posts to be best possible (without invalidating reasonable posted answers). [ask] [help] https://meta.stackoverflow.com/q/261592/3404097 – philipxy Apr 23 '21 at 04:45

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