Engineering Questions with Answers - Multiple Choice Questions

MCQs on Join Expressions

1 - Question

The____condition allows a general predicate over the relations being joined.
a) On
b) Using
c) Set
d) Where

View Answer

Answer: a
Explanation: On gives the condition for the join expression.




2 - Question

Which of the join operations do not preserve non matched tuples?
a) Left outer join
b) Right outer join
c) Inner join
d) Natural join

View Answer

Answer: c
Explanation: INNER JOIN: Returns all rows when there is at least one match in BOTH tables.




3 - Question

SELECT *
  FROM student JOIN takes USING (ID);

The above query is equivalent to
a)

   SELECT *
   FROM student INNER JOIN takes USING (ID);

b)

   SELECT *
   FROM student OUTER JOIN takes USING (ID);

c)

   SELECT *
   FROM student LEFT OUTER JOIN takes USING (ID);

d) None of the mentioned

View Answer

Answer: a
Explanation: Join can be replaced by inner join.




4 - Question

What type of join is needed when you wish to include rows that do not have matching values?
a) Equi-join
b) Natural join
c) Outer join
d) All of the mentioned

View Answer

Answer: c
Explanation: An outer join does not require each record in the two joined tables to have a matching record..




5 - Question

How many tables may be included with a join?
a) One
b) Two
c) Three
d) All of the mentioned

View Answer
Answer: d
Explanation: Join can combine multiple tables.

 




6 - Question

Which are the join types in join condition:
a) Cross join
b) Natural join
c) Join with USING clause
d) All of the mentioned

View Answer

Answer: d
Explanation: There are totally four join types in SQL.




7 - Question

How many join types in join condition:
a) 2
b) 3
c) 4
d) 5

View Answer

Answer: d
Explanation: Types are inner join, left outer join, right outer join, full join, cross join.




8 - Question

Which join refers to join records from the right table that have no matching key in the left table are include in the result set:
a) Left outer join
b) Right outer join
c) Full outer join
d) Half outer join

View Answer

Answer: b
Explanation: RIGHT OUTER JOIN: Return all rows from the right table and the matched rows from the left table.




9 - Question

The operation which is not considered a basic operation of relational algebra is
a) Join
b) Selection
c) Union
d) Cross product

View Answer

Answer: a
Explanation: None.




10 - Question

In SQL the statement select * from R, S is equivalent to
a) Select * from R natural join S
b) Select * from R cross join S
c) Select * from R union join S
d) Select * from R inner join S

View Answer

Answer: b
Explanation: None.

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