In relational algebra, which of the following operators is used to select specific columns (attributes) vertically from a single table while discarding all others?
Consider two union-compatible database relations representing employee records from two different software house branches:
1. 'Lahore_Branch(EmpName, Designation, Age, Salary)'
2. 'Islamabad_Branch(EmpName, Designation, Age, Salary)'
Which relational algebra operation should be applied to find only those employees who work in both branches with identical details, and what is its mathematical representation?
Consider the relations Student(Fname, Lname, MajorCode) and Instructor(First_Name, Last_Name, DeptID) representing university members, where Fname and First_Name, and Lname and Last_Name share compatible character domains respectively. Which of the following statements is correct regarding their relational algebra union-compatibility?
๐ป sql Snippet
-- Relational Set Difference query (Students not Instructors):
SELECT Fname, Lname FROM Student
EXCEPT
SELECT First_Name, Last_Name FROM Instructor;
A.The two relations are not union-compatible since their attribute names differ.
B.The two relations are union-compatible since they have the same type of tuples (same degree and domain-compatible attribute positions).
C.The set operations such as CARTESIAN PRODUCT and DIVISION can be applied on these two relations only if they are union-compatible.
D.To find out the students who are not instructors, it is necessary to perform the operation Student รท Instructor.
Consider two database relations, Student(Fname, Lname, MajorCode) and Instructor(First_Name, Last_Name, DeptID), where Fname and First_Name, Lname and Last_Name share compatible character domains respectively. Which of the following statements is correct regarding their relational algebra set compatibility?
๐ป sql Snippet
-- Relational Set Difference query (Students not Instructors):
SELECT Fname, Lname FROM Student
EXCEPT
SELECT First_Name, Last_Name FROM Instructor;
A.The two relations are not union-compatible because their attribute names are different.
B.The two relations are union-compatible because they share the same degree (number of columns) and domain-compatible attributes (same type of tuples).
C.Set operations like Cartesian Product and Division can only be applied on these relations if they are union-compatible.
D.To find students who are not instructors, we must perform the relational algebra Division operation (Student รท Instructor).
In standard relational database management systems and SQL, what is the precise mathematical behavior and output of a CROSS JOIN (Cartesian Product) executed between two tables, Table_A (containing R rows and C columns) and Table_B (containing S rows and D columns)?
๐ป sql Snippet
SELECT * FROM Table_A CROSS JOIN Table_B;
A.It returns a table containing R + S rows and C + D columns, where unmatched rows are represented as NULL values.
B.It returns a table containing R * S rows and C + D columns, pairing every single row from Table_A with every possible row from Table_B.
C.It returns a table containing only matching rows where Table_A's primary key is identical to Table_B's foreign key.
D.It returns a table with R * S rows and C * D columns, containing only unique non-duplicate rows across both relations.
Consider two database relations: Student(Fname, Lname, MajorCode) and Instructor(First_Name, Last_Name, DeptID), where Fname/First_Name and Lname/Last_Name represent compatible character datatypes. Which of the following statements is correct with respect to the two relations?
๐ป sql Snippet
-- Relational Set Difference query (Students not Instructors):
SELECT Fname, Lname FROM Student
EXCEPT
SELECT First_Name, Last_Name FROM Instructor;
A.The two relations are not union-compatible since their attribute names differ.
B.The two relations are union-compatible since they have the same type of tuples (same degree and domain-compatible attributes).
C.The set operations such as CARTESIAN PRODUCT and DIVISION can be applied on these two relations.
D.To find out the students who are not instructors, it is necessary to perform the operation Student รท Instructor.
Consider two database relations representing members of a university department: Student(Fname, Lname, MajorCode) and Instructor(First_Name, Last_Name, DeptID), where Fname/First_Name and Lname/Last_Name represent compatible character datatypes. Which of the following statements is correct regarding the relational algebra union-compatibility of these two relations?
๐ป sql Snippet
-- Relational Set Difference query (Students not Instructors):
SELECT Fname, Lname FROM Student
EXCEPT
SELECT First_Name, Last_Name FROM Instructor;
A.The two relations are not union-compatible since their attribute names differ.
B.The two relations are union-compatible since they have the same type of tuples (same degree and domain-compatible attribute positions).
C.The set operations such as CARTESIAN PRODUCT and DIVISION can be applied on these two relations only if they are union-compatible.
D.To find out the students who are not instructors, it is necessary to perform the Operation Student รท Instructor.
Consider two database relations representing members of a university department: Student(Fname, Lname, MajorCode) and Instructor(First_Name, Last_Name, DeptID), where Fname/First_Name and Lname/Last_Name represent compatible character datatypes. Which of the following statements is strictly correct regarding the relational algebra union-compatibility of these two relations?
๐ป sql Snippet
-- Relational Set Difference query (Students not Instructors):
SELECT Fname, Lname FROM Student
EXCEPT
SELECT First_Name, Last_Name FROM Instructor;
A.The two relations are not union-compatible because their attribute names are different.
B.The two relations are union-compatible because they share the same degree (number of attributes) and domain-compatible attribute positions (same type of tuples).
C.Set operations like Cartesian Product and Division can only be applied if relations are union-compatible.
D.To find out the students who are not instructors, it is necessary to perform the relational algebra Division operation (Student รท Instructor).
๐ Related CS403 - Database Management Systems Curriculum Units
Continue practicing topic-wise multiple choice questions from adjacent examination units.
