Consider the following statement:S1: Deletion in referencing relation...
S1: Referencing relation is the relation referring to a primary key of some other relation. Deletion in that table will not cause any violation. Hence, no deletion anomaly hence this is true.
So, this statement is true.
S2: This statement is true, since foreign key can be created within a relation
C is a foreign key referring to the primary key "A'' of the same relation R.
S3: S3 is true since count (*) will count the no. of tuples in a relation, on the basis of ID value.
S4: It is true. Since it is possible to decompose every relation into BCNF with lossless join decomposition property but it may or may not preserve the dependencies of the relation.
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Consider the following statement:S1: Deletion in referencing relation...
Analysis of Statements
To evaluate the correctness of the statements, let's consider each one closely:
Statement S1: Deletion in referencing relation causes deletion anomaly.
- This statement is true. Deletion anomalies occur when the deletion of a tuple in a relation leads to unintended loss of data in other related tuples. For example, if you delete a customer who has orders, you may inadvertently lose all information about their orders if it's not properly handled.
Statement S2: Referential integrity constraints are specified between exactly two relations in a schema.
- This statement is false. Referential integrity constraints can exist between more than two relations. A foreign key in one relation can reference a primary key in another, but it can also be part of a more complex relationship involving multiple tables.
Statement S3: Count(*) also counts the tuples which consist of NULL in a relation.
- This statement is false. The Count(*) function counts all the rows in a table, regardless of whether they contain NULL values. However, if we use Count(column_name), it will not count rows where that specific column is NULL.
Statement S4: Every relation is possible to decompose into BCNF with dependency preserving and lossless join decomposition.
- This statement is false. While every relation can be decomposed into BCNF, it is not always possible to do so while preserving all functional dependencies and ensuring a lossless join. Some decompositions may lose dependencies or may not be lossless.
Conclusion
- Since S2, S3, and S4 are false, and S1 is true, the correct answer is option 'D': All are false. However, S1 is actually true, indicating that the correct answer should be reconsidered based on the evaluation of S1.