Computer Science

SQL Basics, DDL & Table Creation MCQs | 25 Practice Questions with Answers | CBSE Class 12 Computer Science

Class 12 · Computer Science

SQL Basics, DDL & Table Creation MCQs (25 Questions)

Practice these multiple-choice questions to strengthen your understanding of SQL Basics, Data Definition Language (DDL), Data Manipulation Language (DML), Data Types, Constraints, and Table Creation. Click Show Answer to reveal the correct answer and explanation.

Q1. What does SQL stand for?

A. Structured Query Language
B. Simple Query Language
C. Standard Question Language
D. Structured Queue Language

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Answer: A. Structured Query Language

Explanation: SQL (Structured Query Language) is the standard language used to create, manage, and manipulate relational databases.

Q2. SQL is mainly used to:

A. Design graphics
B. Manage databases
C. Develop operating systems
D. Create animations

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Answer: B. Manage databases

Explanation: SQL is used to create databases, retrieve, insert, update, and delete data.

Q3. Which SQL category is used to create and modify database objects?

A. DML
B. DDL
C. DCL
D. TCL

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Answer: B. DDL

Explanation: Data Definition Language (DDL) is used to define database structures such as databases and tables.

Q4. Which SQL category is used to insert, update, and delete records?

A. DML
B. DDL
C. DCL
D. TCL

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Answer: A. DML

Explanation: Data Manipulation Language (DML) is used to manipulate the data stored in tables.

Q5. Which SQL command creates a new database?

A. NEW DATABASE
B. CREATE DATABASE
C. ADD DATABASE
D. MAKE DATABASE

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Answer: B. CREATE DATABASE

Explanation: The CREATE DATABASE statement creates a new database.

Q6. Which SQL command selects a database for use?

A. OPEN DATABASE
B. SELECT DATABASE
C. USE
D. CONNECT

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Answer: C. USE

Explanation: The USE command selects the database on which SQL operations will be performed.

Q7. Which command displays all available databases?

A. SHOW DATABASES
B. DISPLAY DATABASES
C. LIST DATABASES
D. SHOW DB

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Answer: A. SHOW DATABASES

Explanation: The SHOW DATABASES command displays the list of all databases.

Q8. Which SQL command permanently removes a database?

A. DELETE DATABASE
B. REMOVE DATABASE
C. DROP DATABASE
D. ERASE DATABASE

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Answer: C. DROP DATABASE

Explanation: The DROP DATABASE command permanently deletes a database.

Q9. Which command displays all tables in the selected database?

A. SHOW TABLES
B. DISPLAY TABLES
C. LIST TABLES
D. SHOW ALL TABLES

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Answer: A. SHOW TABLES

Explanation: The SHOW TABLES command lists all tables in the currently selected database.

Q10. Which SQL command is used to create a table?

A. MAKE TABLE
B. CREATE TABLE
C. NEW TABLE
D. ADD TABLE

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Answer: B. CREATE TABLE

Explanation: The CREATE TABLE statement is used to create a new table in the selected database.

Q11. Which SQL command displays the structure of a table?

A. SHOW TABLE
B. DESCRIBE TABLE
C. DESCRIBE
D. VIEW TABLE

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Answer: C. DESCRIBE

Explanation: The DESCRIBE (or DESC) command displays the structure of a table, including column names, data types, and constraints.

Q12. Which SQL data type is used to store fixed-length character strings?

A. VARCHAR(n)
B. CHAR(n)
C. INT
D. FLOAT

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Answer: B. CHAR(n)

Explanation: CHAR(n) stores fixed-length character strings. If the entered value is shorter than n, spaces are added automatically.

Q13. Which SQL data type is used to store variable-length character strings?

A. CHAR(n)
B. INT
C. VARCHAR(n)
D. DATE

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Answer: C. VARCHAR(n)

Explanation: VARCHAR(n) stores variable-length strings up to the specified maximum length.

Q14. Which SQL data type is used to store whole numbers?

A. FLOAT
B. DATE
C. INT
D. CHAR

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Answer: C. INT

Explanation: The INT data type stores integer (whole number) values.

Q15. Which SQL data type is used to store decimal values?

A. CHAR
B. FLOAT
C. DATE
D. VARCHAR

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Answer: B. FLOAT

Explanation: The FLOAT data type stores real (decimal) numbers.

Q16. Which SQL data type is used to store dates?

A. TIME
B. DATE
C. YEAR
D. DATETIME

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Answer: B. DATE

Explanation: The DATE data type stores date values in the format supported by the DBMS.

Q17. Which constraint prevents NULL values in a column?

A. UNIQUE
B. PRIMARY KEY
C. NOT NULL
D. DEFAULT

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Answer: C. NOT NULL

Explanation: The NOT NULL constraint ensures that a column must always contain a value.

Q18. Which constraint ensures that all values in a column are different?

A. PRIMARY KEY
B. UNIQUE
C. NOT NULL
D. FOREIGN KEY

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Answer: B. UNIQUE

Explanation: The UNIQUE constraint prevents duplicate values in a column.

Q19. Which constraint uniquely identifies each record in a table?

A. UNIQUE
B. NOT NULL
C. PRIMARY KEY
D. DEFAULT

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Answer: C. PRIMARY KEY

Explanation: A PRIMARY KEY uniquely identifies every record in a table and cannot contain NULL values.

Q20. Which of the following SQL statements correctly creates a table?

CREATE TABLE Student
(
RollNo INT PRIMARY KEY,
Name VARCHAR(30),
Marks FLOAT
);

A. Correct SQL statement
B. Missing semicolon after CREATE TABLE
C. PRIMARY KEY cannot be used with INT
D. VARCHAR cannot store names

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Answer: A. Correct SQL statement

Explanation: This is a valid SQL statement that creates a table named Student with appropriate data types and a primary key.

Q21. Which SQL statement selects the SchoolDB database for use?

A. OPEN SchoolDB;
B. SELECT DATABASE SchoolDB;
C. USE SchoolDB;
D. CONNECT SchoolDB;

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Answer: C. USE SchoolDB;

Explanation: The USE statement selects the database on which subsequent SQL commands will be executed.

Q22. Which SQL command displays the names of all tables in the currently selected database?

A. SHOW TABLES;
B. SHOW DATABASES;
C. DESCRIBE TABLES;
D. DISPLAY TABLES;

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Answer: A. SHOW TABLES;

Explanation: The SHOW TABLES; command lists all tables present in the selected database.

Q23. Which SQL statement correctly displays the structure of the Student table?

A. SHOW Student;
B. DESCRIBE Student;
C. VIEW Student;
D. SHOW STRUCTURE Student;

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Answer: B. DESCRIBE Student;

Explanation: The DESCRIBE (or DESC) command displays the structure of a table, including its columns, data types, and constraints.

Q24. Which of the following SQL statements is correct?

A. CREATE DATABASE SchoolDB;
B. USE SchoolDB;
C. CREATE TABLE Student (...);
D. All of these.

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Answer: D. All of these.

Explanation: All the given SQL statements are valid and commonly used while creating and working with databases and tables.

Q25. Which statement about SQL and DDL is correct?

A. SQL is used to communicate with relational databases.
B. DDL commands define the structure of databases and tables.
C. PRIMARY KEY uniquely identifies each record in a table.
D. All of these.

Show Answer

Answer: D. All of these.

Explanation: SQL is the standard language for relational databases. DDL commands create and define database objects, and the primary key uniquely identifies each record.

Answer Key

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	A	10	B	19	C
2	B	11	C	20	A
3	B	12	B	21	C
4	A	13	C	22	A
5	B	14	C	23	B
6	C	15	B	24	D
7	A	16	B	25	D
8	C	17	C
9	A	18	B

Practice Tips

Remember the purpose of SQL:
- SQL (Structured Query Language) is used to create, manage, and manipulate relational databases.
Differentiate between SQL command categories:
- DDL (Data Definition Language) – Defines database structure (e.g., CREATE, DROP).
- DML (Data Manipulation Language) – Manipulates data stored in tables (e.g., INSERT, UPDATE, DELETE).
Revise the commonly used SQL data types:
- CHAR(n) – Fixed-length character string.
- VARCHAR(n) – Variable-length character string.
- INT – Integer values.
- FLOAT – Decimal values.
- DATE – Date values.
Understand the purpose of SQL constraints:
- NOT NULL – Does not allow NULL values.
- UNIQUE – Prevents duplicate values.
- PRIMARY KEY – Uniquely identifies each record and cannot contain NULL values.
Memorize these frequently used SQL commands:
- CREATE DATABASE
- USE
- SHOW DATABASES
- DROP DATABASE
- SHOW TABLES
- CREATE TABLE
- DESCRIBE / DESC
Practice writing simple SQL statements and identifying syntax errors, as SQL syntax-based questions are commonly asked in CBSE board examinations.

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	A	10	B	19	C
2	B	11	C	20	A
3	B	12	B	21	C
4	A	13	C	22	A
5	B	14	C	23	B
6	C	15	B	24	D
7	A	16	B	25	D
8	C	17	C
9	A	18	B

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	A	10	B	19	C
2	B	11	C	20	A
3	B	12	B	21	C
4	A	13	C	22	A
5	B	14	C	23	B
6	C	15	B	24	D
7	A	16	B	25	D
8	C	17	C
9	A	18	B

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	A	10	B	19	C
2	B	11	C	20	A
3	B	12	B	21	C
4	A	13	C	22	A
5	B	14	C	23	B
6	C	15	B	24	D
7	A	16	B	25	D
8	C	17	C
9	A	18	B