Database-MySQL [3i Infotech Placement]: Sample Questions 10 - 12 of 162
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Question 11
Explanation
- Minimal key can identify each tuple of the relation schema uniquely.
- For finding the minimal key- find the closure that is the set of all attributes dependent on any given set of attributes under the given set of functional dependency.
Algo I
I Determining , closure for X, given set of FDs F
1. Set
2. Set Old
3. For each FD Y Z in F and if Y belongs to then add Z to
4. Repeat steps 2 and 3 until Old
Algo. II
Determining minimal K for relation schema R, given set of FDs F
1. Set K to R that is make K a set of all attributes in R
2. For each attribute A in K
a. Compute with respect to
b. If then set
Question 12
Explanation
- A DBMS maintains information about each of relation and index that it contains.
- The metadata is the information stored in a collection of relations maintained by the system
- It is also called data dictionary.
- The catalog relations are also called the system catalog or the data dictionary.
- The system catalog is sometimes also referred to as metadata (data about data) .
- The system catalog is generally used only for query optimization.
- It is also known as metadata.