2. Suppose that two columns in two different tables have the same column name. W

Question

2. Suppose that two columns in two different tables have the same column name. What convention is used to give each a unique name?

3. Explain the three different set of terms used to describe tables, columns, and rows.

4. Under what conditions will a determinant be unique in a relation?

5. When would you use a surrogate key?

6. Which normal forms are concerned with functional dependencies?

7. What conditions are required for a relation to be in 2NF?

8. What conditions are required for a relation to be in 3NF?

9. What conditions are required for a relation to be in BCNF?

10. What normal form is concerned with multivalued dependencies?

11. Consider the relation:
PERSON(Name, Sibling, ShoeSize, Hobby)
Assume that the following functional dependencies exist:
Name ?? Sibling
Name ? ShoeSize
Name ?? Hobby

Place the PERSON relation in 4NF.

Explanation / Answer

3) The three different sets of names used to describe tables, columns, and rows are relations, fields, and records respectively. Tables, columns, and rows can also be named as Relations, attributes, and tuples respectively. 5) A surrogate key is used when uniqueness within a database table is needed. It is a substitution of natural primary key 6) Second, third and boyce-codd normal forms are the normal forms concerned with functional dependencies. 7) The conditions required for a relation to be in 2NF are: • It is in1NF • All its non-prime attributes must be functionally dependent on the whole of every candidate key 8) The conditions required for a relation to be in 3NF are: • The relation is in 2NF • Every non-prime attribute of the relation is non-transitively dependent on every candidate key of the relation 9) The condition required for a relation to be in BCNF is, the relation must have at least one candidate key without nulls. 10) Fourth normal form is concerned with multivalued dependencies

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