Databases and SQL Quiz - CBSE Class 12 Computer Science

Free practice quiz: Databases and SQL (CBSE Class 12 Computer Science). 16 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. Which SQL command is used to retrieve data from a database?

   1. SELECT
   2. INSERT
   3. UPDATE
   4. DELETE
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   Answer: A. SELECT

   The SELECT statement is used to query data from a database. INSERT adds data, UPDATE modifies data, and DELETE removes data.

2. Explain the difference between INNER JOIN and LEFT JOIN in SQL.

   1. INNER JOIN returns all rows from both tables, LEFT JOIN only returns matching rows.
   2. INNER JOIN returns only matching rows, LEFT JOIN returns all rows from the left table and matching rows from the right.
   3. INNER JOIN returns all rows from the right table, LEFT JOIN returns all rows from the left table.
   4. There is no difference between INNER JOIN and LEFT JOIN.
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   Answer: B. INNER JOIN returns only matching rows, LEFT JOIN returns all rows from the left table and matching rows from the right.

   INNER JOIN only includes rows where there is a match in both tables. LEFT JOIN includes all rows from the left table, even if there's no match in the right table.

3. What is a relational database management system (RDBMS)?

   1. A system for managing data stored in flat files.
   2. A system for managing data stored in a network model.
   3. A system for managing data stored in a hierarchical model.
   4. A system for managing data stored in relations (tables).
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   Answer: D. A system for managing data stored in relations (tables).

   RDBMS organizes data into tables with rows and columns, establishing relationships between tables for efficient data management and retrieval.

4. Explain the concept of ACID properties in database transactions.

   1. Atomicity, Consistency, Isolation, Durability
   2. Accuracy, Consistency, Integrity, Dependability
   3. Atomicity, Coherency, Isolation, Durability
   4. Accuracy, Coherency, Integrity, Dependability
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   Answer: A. Atomicity, Consistency, Isolation, Durability

   ACID properties (Atomicity, Consistency, Isolation, Durability) ensure reliable database transactions. Atomicity means all or nothing; Consistency maintains data integrity; Isolation prevents interference; Durability ensures data persistence.

5. What is the purpose of the WHERE clause in an SQL SELECT statement?

   1. To specify the columns to be retrieved
   2. To sort the results
   3. To filter the rows based on a condition
   4. To group the rows
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   Answer: C. To filter the rows based on a condition

   The WHERE clause is used to filter the rows in a SQL SELECT statement, returning only the rows that satisfy a specified condition.

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