This is the DBMS questions and answers section on "Joins" with explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand.
1. The____condition allows a general predicate over the relations being joined.
Answer: Option A
Explanation:
On
On gives the condition for the join expression.
2. Which of the join operations do not preserve non matched tuples.
- A. Left outer join
- B. Right outer join
- C. Inner join
Answer: Option C
Explanation:
Inner join
INNER JOIN: Returns all rows when there is at least one match in BOTH tables
3. 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
Answer: Option C
Explanation:
Outer join
An outer join does not require each record in the two joined tables to have a matching record.
4. How many tables may be included with a join?
- A. One
- B. Two
- C. Three
- D. All of the mentioned
Answer: Option D
Explanation:
All of the mentioned
Join can combine multiple tables.
5. Which are the join types in join condition:
- A. Cross join
- B. Natural join
- C. Join with USING clause
- D. All of the mentioned
Answer: Option D
Explanation:
All of the mentioned
There are totally four join types in SQL.
