2nd year Chapter 4 Data Integrity And Normalization Question And Answer
Short AN Simple Questions and Answer
Q1: What is entity integrity?
Ans: Entity integrity is a constraint on entities in a database. It states that every table must have a primary key, and the chosen primary key columns should be unique and not null. This rule ensures that duplicate rows are not allowed, and each value in the primary key can uniquely identify all rows in a table.
Q2: What is referential integrity?
Ans: Referential integrity is a constraint on foreign keys in a database. It ensures that if a foreign key exists in a relation, either the foreign key value must match the primary key value of a tuple in its parent table, or the foreign key value must be completely NULL.
Q3: What is redundancy?
Ans: Redundancy occurs when the same data values are stored more than once in a table or in multiple tables.
Q4: What is normalization?
Ans: Normalization is the process of converting complex data structures into simpler and more stable structures. It involves reviewing the entities and their attributes to ensure that attributes are stored where they belong. This process aims to eliminate data redundancy and analyze attribute dependencies within entities.
Q5: What is a repeating group?
Ans: A repeating group is a set of one or more data items that can occur a variable number of times within a tuple.
Q6: What are database anomalies?
Ans: Database anomalies are situations that arise when records are inserted, modified, or deleted in a database, causing the database to become inconsistent or incorrect.
Q7: What is an insertion anomaly?
Ans: An insertion anomaly occurs when a new record cannot be inserted without having additional facts about another entity. It restricts the ability to insert data.
Q8: What is a deletion anomaly?
Ans: A deletion anomaly occurs when the deletion of a record leads to the unintentional deletion of facts about another entity, making the database inconsistent.
Q9: What is a modification anomaly?
Ans: A modification anomaly occurs when modifying the value of a specific attribute in one record requires modifying the same value in multiple records, potentially leading to inconsistency.
Q10: What is a partial dependency?
Ans: Partial dependency is a type of dependency in which one or more non-key attributes are functionally dependent on a part of the primary key.
Q11: What is a transitive dependency?
Ans: Transitive dependency is a type of functional dependency in which a non-key attribute depends on another non-key attribute, creating a chain of dependencies.
Q12: What is an integrity constraint?
Ans: Integrity constraints are rules designed to maintain the correctness and consistency of data in a database. They ensure that the data meets specific quality and consistency standards.
Q13: What is 1st Normal form? Ans: A relation is in 1st normal form if all its domain values are atomic, meaning each cell contains only one value, and there are no repeating groups within the relation.
Q14: What is 2nd Normal form?
Ans: A relation is in the 2nd normal form if it meets the criteria of 1st normal form and every non-key attribute is fully functionally dependent on the primary key. In other words, all non-key attributes must depend solely on the primary key.
Q15: What is the 3rd Normal form?
Ans: A relation is in 3rd normal form if it meets the criteria of 2nd normal form and has no transitive dependencies. Transitive dependencies refer to functional dependencies between non-key attributes, and these should be eliminated for a relation to be in 3rd normal form.