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Here is the table descriptions:

Students

SID SNAME
1 Adams
2 Jones
3 Smith
4 Baker

Teachers

TID TNAME
60192 Howser
45869 Langley

Classes

CID CNAME
IS318 Database
IS301 Java

Student info:

SID CID TID Grade
1 IS318 60192 A
1 IS301 45869 B
2 IS318 60192 A
3 IS318 60192 B
4 IS301 45869 A
4 IS318 60192 A

SID and CID, Composite primary key. SID,CID -> Grade and SID,TID -> Grade.

Is the table still in 3NF

philipxy
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Shanmukha Reddy
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    Can teachers teach more than a single class? If so, seems `SID, CID, TID` needed in final table. If not, seems `TID` belongs in Classes instead. – Damien_The_Unbeliever Nov 08 '21 at 15:17
  • Teachers don't teach more than a single class. Got it. – Shanmukha Reddy Nov 08 '21 at 15:21
  • It is not clear what your reasoning is or what your question is. Use enough words, sentences & references to parts of examples to clearly & fully say what you mean. Quote a definition of 3NF & the terms it uses & the terms they use etc then clearly explain why you think 3NF is or isn't met. PS What matters is what the definition says, not other things you might happen to notice. Why would they matter to evaluating the definition condition? (Rhetorical.) PS Please put everything needed to ask your question in the post body, not just the title. PS Clarify via edits, not comments. – philipxy Nov 08 '21 at 20:30
  • 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 Nov 08 '21 at 20:33
  • See my comment on the accepted answer, which is wrong. – philipxy Nov 08 '21 at 20:37

1 Answers1

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Not as far as I understand it:

A database relation (e.g. a database table) is said to meet third normal form standards if all the attributes (e.g. database columns) are functionally dependent on solely the primary key.

https://en.wikipedia.org/wiki/Third_normal_form

Since your attribute is not solely dependent on the primary key, then I think not.

Chris Strickland
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