1. Which SQL statement is used to return the number of rows in a table?
A. SELECT COUNT()
B. SELECT SUM()
C. SELECT MAX()
D. SELECT MIN()
Answer: A) SELECT COUNT()
Rationale: The COUNT() function is used to return the number of rows in a table.
2. Which of the following is a non-relational database?
A. MySQL
B. PostgreSQL
C. MongoDB
D. Oracle
Answer: C) MongoDB
Rationale: MongoDB is a non-relational (NoSQL) database, which stores data in JSON-like
documents rather than relational tables.
3. What is a foreign key?
A. A primary key in a different table
,B. A key that uniquely identifies records in the current table
C. A key used for indexing the database
D. A key used to sort the records
Answer: A) A primary key in a different table
Rationale: A foreign key is a field in one table that uniquely identifies a row in another table.
4. What is the purpose of the EXPLAIN keyword in SQL?
A. To display the execution plan for a query
B. To explain the database schema
C. To summarize the table structure
D. To explain error messages
Answer: A) To display the execution plan for a query
Rationale: The EXPLAIN keyword is used to display the execution plan for a SQL query,
helping to analyze and optimize query performance.
5. Which of the following is NOT an advantage of normalization?
A. Reduces redundancy
B. Increases data integrity
C. Makes the database more complex
D. Improves query performance
Answer: C) Makes the database more complex
, Rationale: Normalization reduces redundancy, improves integrity, but may make the database
more complex with multiple tables.
6. In SQL, which of the following is used to retrieve unique values from a column?
A. SELECT ALL
B. DISTINCT
C. UNIQUE
D. LIMIT
Answer: B) DISTINCT
Rationale: The DISTINCT keyword is used to retrieve unique values from a column.
7. Which SQL command is used to update data in a table?
A. INSERT
B. UPDATE
C. DELETE
D. SELECT
Answer: B) UPDATE
Rationale: The UPDATE command is used to modify existing records in a table.
8. What does the SQL keyword LIMIT do?
A. Restricts the number of records returned
A. SELECT COUNT()
B. SELECT SUM()
C. SELECT MAX()
D. SELECT MIN()
Answer: A) SELECT COUNT()
Rationale: The COUNT() function is used to return the number of rows in a table.
2. Which of the following is a non-relational database?
A. MySQL
B. PostgreSQL
C. MongoDB
D. Oracle
Answer: C) MongoDB
Rationale: MongoDB is a non-relational (NoSQL) database, which stores data in JSON-like
documents rather than relational tables.
3. What is a foreign key?
A. A primary key in a different table
,B. A key that uniquely identifies records in the current table
C. A key used for indexing the database
D. A key used to sort the records
Answer: A) A primary key in a different table
Rationale: A foreign key is a field in one table that uniquely identifies a row in another table.
4. What is the purpose of the EXPLAIN keyword in SQL?
A. To display the execution plan for a query
B. To explain the database schema
C. To summarize the table structure
D. To explain error messages
Answer: A) To display the execution plan for a query
Rationale: The EXPLAIN keyword is used to display the execution plan for a SQL query,
helping to analyze and optimize query performance.
5. Which of the following is NOT an advantage of normalization?
A. Reduces redundancy
B. Increases data integrity
C. Makes the database more complex
D. Improves query performance
Answer: C) Makes the database more complex
, Rationale: Normalization reduces redundancy, improves integrity, but may make the database
more complex with multiple tables.
6. In SQL, which of the following is used to retrieve unique values from a column?
A. SELECT ALL
B. DISTINCT
C. UNIQUE
D. LIMIT
Answer: B) DISTINCT
Rationale: The DISTINCT keyword is used to retrieve unique values from a column.
7. Which SQL command is used to update data in a table?
A. INSERT
B. UPDATE
C. DELETE
D. SELECT
Answer: B) UPDATE
Rationale: The UPDATE command is used to modify existing records in a table.
8. What does the SQL keyword LIMIT do?
A. Restricts the number of records returned
