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Question

Consider a relational schema team(name, city, owner), with functional dependencies {name $\to$ city, name $\to$ owner}.

The relation team is decomposed into two relations, t1(name, city) and t2(name, owner). Which of the following statement(s) is/are TRUE?

To solve this problem, we need to evaluate the relational schema \(\text{team(name, city, owner)}\) with the given functional dependencies and assess the decomposition into relations \(\text{t1(name, city)}\) and \(\text{t2(name, owner)}\).

Step 1: Evaluate the normalization of the relation team.

  • The given functional dependencies are:
    • \(\text{name} \rightarrow \text{city}\)
    • \(\text{name} \rightarrow \text{owner}\)
  • Since \(\text{name}\) is the only determinant for the attributes \(\text{city}\) and \(\text{owner}\), it implies that \(\text{name}\) is a candidate key for the relation.
  • Every determinant is a candidate key, so the relation is in BCNF. However, since every relation in BCNF is also in 3NF, the relation is also in 3NF.

Step 2: Check the decomposed relations t1 and t2.

  • Relation t1(name, city):
    • Functional dependency: \(\text{name} \rightarrow \text{city}\)
    • \(\text{name}\) is a candidate key for this relation. Therefore, it is in BCNF.
  • Relation t2(name, owner):
    • Functional dependency: \(\text{name} \rightarrow \text{owner}\)
    • \(\text{name}\) is a candidate key for this relation. Therefore, it is in BCNF.

Step 3: Check for lossless join property.

  • The original relation team can be reconstructed from the decomposed relations t1 and t2 using the common attribute \(\text{name}\) which is a key in both decompositions.
  • Since the decomposition is based on projecting the attributes determined by \(\text{name}\), the join is lossless because it is a projection join.

Conclusion:

  • The relations t1 and t2 are in BCNF.
  • The decomposition is lossless because the projections on \(\text{name}\) allows the original table to be reconstructed without loss of data.
  • The statement \(\text{"The relations t1 and t2 are in BCNF"}\) is true.
  • The statement \(\text{"The decomposition constitutes a lossless join"}\) is also true.
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Important Questions from Normal Form

  1. Which of the following statement(s) is/are correct regarding a relation in second normal form?

    I. It is in first normal form

    II. Every non-key attribute is fully and functionally independent on the primary key

  2. Which of the following normal forms specifically addresses and eliminates partial dependencies?

  3. In a relational database, which one of the following is CORRECT:
     

  4. Which of the following is false ?

  5. The Relation

    Vendor Order (V_no, V_ord_no, V_name, Qty_sup, unit_price)

    is in 2NF because :

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