Database Fundamentals Chapter 4 - Set 1

What is SQL primarily used for?

• Managing spreadsheets.

• Managing and manipulating relational databases.

• Managing user permissions in the operating system.

• Creating visual designs.

Answer explanation

SQL is primarily used for managing and manipulating relational databases, allowing users to create, read, update, and delete data efficiently. The other options do not accurately describe SQL's main function.

Which of the following is a SQL command used to retrieve data from a database?

• INSERT

• SELECT

• DELETE

• ALTER

Answer explanation

The SQL command used to retrieve data from a database is 'SELECT'. The other options serve different purposes: 'INSERT' adds data, 'DELETE' removes data, and 'ALTER' modifies database structures.

What type of SQL commands are used to create and manage the structure of database objects like tables and indexes?

• Data Definition Language (DDL)

• Data Manipulation Language (DML)

• Data Control Language (DCL)

• Transaction Control Language (TCL)

Answer explanation

The correct choice is Data Definition Language (DDL), which is used to create and manage the structure of database objects like tables and indexes. DDL commands include CREATE, ALTER, and DROP.

Which of the following is a DML command?

• CREATE

• GRANT

• SELECT

• COMMIT

Answer explanation

The correct choice is SELECT, which is a Data Manipulation Language (DML) command used to retrieve data from a database. CREATE, GRANT, and COMMIT are not DML commands; they serve different purposes in SQL.

What is the role of Data Control Language (DCL) in SQL?

• Defining and managing database structure.

• Managing permissions and security in a database.

• Performing CRUD operations on database data.

• Managing transactions.

Answer explanation

Data Control Language (DCL) is used to manage permissions and security in a database, allowing administrators to grant or revoke access rights to users. This is crucial for maintaining data integrity and security.

Which SQL command is used to permanently save changes made during a transaction?

• SAVEPOINT

• ROLLBACK

• COMMIT

• GRANT

Answer explanation

The COMMIT command is used to permanently save all changes made during a transaction in SQL. Unlike ROLLBACK, which undoes changes, COMMIT finalizes them, ensuring data integrity.

Which of the following is not a category of SQL statements?

• Data Control Language (DCL)

• Data Processing Language (DPL)

• Data Definition Language (DDL)

• Transaction Control Language (TCL)

Answer explanation

Data Processing Language (DPL) is not a recognized category of SQL statements. The main categories include Data Control Language (DCL), Data Definition Language (DDL), and Transaction Control Language (TCL).

Which SQL command is used to modify an existing database structure, such as adding a column to a table?

• CREATE

• DROP

• ALTER

• TRUNCATE

Answer explanation

The SQL command 'ALTER' is used to modify an existing database structure, such as adding a column to a table. In contrast, 'CREATE' is for creating new structures, 'DROP' removes them, and 'TRUNCATE' deletes all rows in a table.

What type of constraint ensures that a column cannot have NULL values?

• UNIQUE

• CHECK

• PRIMARY KEY

• NOT NULL

Answer explanation

The NOT NULL constraint ensures that a column cannot contain NULL values, enforcing that every row must have a valid entry for that column. This is the correct choice for preventing NULLs.

Which constraint is used to ensure that the values in a column or a set of columns are unique across all rows in the table?

• FOREIGN KEY

• UNIQUE

• NOT NULL

• CHECK

Answer explanation

The UNIQUE constraint ensures that all values in a column or a set of columns are distinct across all rows in the table, preventing duplicate entries. This is essential for maintaining data integrity.