Mastering SQL Concepts

What is the purpose of the SELECT statement in SQL?

• To update existing records in a database.

• To delete data from a database.

• To create new tables in a database.

• To retrieve data from a database.

What is normalization in databases and why is it important?

• Normalization is important because it minimizes data redundancy, prevents data anomalies, and enhances data integrity, making the database more efficient and easier to maintain.

• Normalization has no impact on data integrity or efficiency.

• Normalization is only necessary for small databases.

• Normalization increases data redundancy and complexity.

List the different types of normalization forms.

• 1NF, 3NF, 4NF, 5NF, 6NF

• 1NF, 2NF, 3NF, BCNF, 4NF, 5NF

• 1NF, 2NF, 3NF, 4NF, 5NF, 7NF

• 1NF, 2NF, 3NF, 6NF

What are the common data types used in SQL?

• TIMESTAMP

• FLOAT

• CHAR

• INTEGER, VARCHAR, DATE, BOOLEAN

How do you define a primary key in a SQL table?

• A primary key is automatically created for every table in SQL.

• A primary key is defined using the PRIMARY KEY constraint in a SQL table.

• A primary key is defined using the UNIQUE constraint in a SQL table.

• A primary key can be any column in a SQL table without restrictions.

What is an index in a database and why is it used?

• An index is a data structure that improves the speed of data retrieval in a database.

• An index is a method for encrypting database information.

• An index is used to store backup copies of data.

• An index is a type of database table.

What SQL command is used to remove a table from a database?

• REMOVE TABLE

• DROP TABLE

• DELETE TABLE

• CLEAR TABLE

How can you retrieve unique values from a column in SQL?

• SELECT column_name FROM table_name WHERE column_name IS NOT NULL;

• SELECT column_name FROM table_name GROUP BY column_name;

• SELECT UNIQUE column_name FROM table_name;

• SELECT DISTINCT column_name FROM table_name;

What is a foreign key and how does it relate to primary keys?

• A foreign key is a field that cannot be null.

• A foreign key is a field that links to a primary key in another table, establishing a relationship between the two.

• A foreign key is a unique identifier for a table.

• A foreign key is a type of primary key.

Explain the concept of data integrity in databases.

• Data integrity refers to the speed of data retrieval in databases.

• Data integrity ensures the accuracy and consistency of data in a database.

• Data integrity ensures that data is stored in multiple formats.

• Data integrity is the process of backing up data regularly.