Chapter 21 - Appendix B: SQL Interview Questions

This appendix compiles common SQL interview questions, which touch on both basic and advanced aspects of SQL. They cover diverse topics, such as basic commands, joins, indexes, stored procedures, and more.

Let's get started:

1. What does SQL stand for, and what is it used for?

   SQL stands for Structured Query Language. It is a standard language used for interacting with relational databases. SQL can be used to insert, search, update, and delete database records. It can't write complete applications, but it allows you to manage data in databases.

2. What are the differences between SQL and NoSQL?

   SQL databases are relational, NoSQL are non-relational. SQL databases use structured query language and have a predefined schema. NoSQL databases have dynamic schemas for unstructured data.

3. Can you explain the basic types of SQL commands?

   SQL commands can be divided into five types based on their functionality: DDL (Data Definition Language), DML (Data Manipulation Language), DCL (Data Control Language), TCL (Transaction Control Language), and DQL (Data Query Language).

4. What is the difference between DELETE and TRUNCATE commands?

   DELETE is a DML command and TRUNCATE is a DDL command. DELETE statement is used to delete a row in a table. TRUNCATE statement is a Data Definition Language (DDL) operation that is used to mark the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms intended to protect the data.

5. What is a JOIN in SQL? Can you explain different types of JOIN?

   JOIN is a means for combining columns from one (self-join) or more tables by using values common to each. ANSI-standard SQL specifies five types of JOIN: INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS.

6. What is the use of the DISTINCT keyword in SQL?

   DISTINCT keyword in SQL is used to return only distinct (unique) values in the result set. It eliminates all the duplicate records.

7. What are Indexes in SQL?

   Indexes are used to retrieve data from databases more quickly. Indexes are used on columns for faster search operations.

8. What is a View in SQL?

   A View is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

9. What is a Stored Procedure?

   A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again. It can take in parameters and can return a value.

10. What is a Trigger in SQL?

    A trigger in SQL is a special type of stored procedure that automatically runs when an event occurs in the database server.

Like with Python, these are just examples, and the actual questions you'll be asked can vary greatly depending on the specific role and company. Always study the job description to understand which concepts and skills are most important.

This appendix compiles common SQL interview questions, which touch on both basic and advanced aspects of SQL. They cover diverse topics, such as basic commands, joins, indexes, stored procedures, and more.

Let's get started:

1. What does SQL stand for, and what is it used for?

   SQL stands for Structured Query Language. It is a standard language used for interacting with relational databases. SQL can be used to insert, search, update, and delete database records. It can't write complete applications, but it allows you to manage data in databases.

2. What are the differences between SQL and NoSQL?

   SQL databases are relational, NoSQL are non-relational. SQL databases use structured query language and have a predefined schema. NoSQL databases have dynamic schemas for unstructured data.

3. Can you explain the basic types of SQL commands?

   SQL commands can be divided into five types based on their functionality: DDL (Data Definition Language), DML (Data Manipulation Language), DCL (Data Control Language), TCL (Transaction Control Language), and DQL (Data Query Language).

4. What is the difference between DELETE and TRUNCATE commands?

   DELETE is a DML command and TRUNCATE is a DDL command. DELETE statement is used to delete a row in a table. TRUNCATE statement is a Data Definition Language (DDL) operation that is used to mark the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms intended to protect the data.

5. What is a JOIN in SQL? Can you explain different types of JOIN?

   JOIN is a means for combining columns from one (self-join) or more tables by using values common to each. ANSI-standard SQL specifies five types of JOIN: INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS.

6. What is the use of the DISTINCT keyword in SQL?

   DISTINCT keyword in SQL is used to return only distinct (unique) values in the result set. It eliminates all the duplicate records.

7. What are Indexes in SQL?

   Indexes are used to retrieve data from databases more quickly. Indexes are used on columns for faster search operations.

8. What is a View in SQL?

   A View is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

9. What is a Stored Procedure?

   A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again. It can take in parameters and can return a value.

10. What is a Trigger in SQL?

    A trigger in SQL is a special type of stored procedure that automatically runs when an event occurs in the database server.

Like with Python, these are just examples, and the actual questions you'll be asked can vary greatly depending on the specific role and company. Always study the job description to understand which concepts and skills are most important.

This appendix compiles common SQL interview questions, which touch on both basic and advanced aspects of SQL. They cover diverse topics, such as basic commands, joins, indexes, stored procedures, and more.

Let's get started:

1. What does SQL stand for, and what is it used for?

   SQL stands for Structured Query Language. It is a standard language used for interacting with relational databases. SQL can be used to insert, search, update, and delete database records. It can't write complete applications, but it allows you to manage data in databases.

2. What are the differences between SQL and NoSQL?

   SQL databases are relational, NoSQL are non-relational. SQL databases use structured query language and have a predefined schema. NoSQL databases have dynamic schemas for unstructured data.

3. Can you explain the basic types of SQL commands?

   SQL commands can be divided into five types based on their functionality: DDL (Data Definition Language), DML (Data Manipulation Language), DCL (Data Control Language), TCL (Transaction Control Language), and DQL (Data Query Language).

4. What is the difference between DELETE and TRUNCATE commands?

   DELETE is a DML command and TRUNCATE is a DDL command. DELETE statement is used to delete a row in a table. TRUNCATE statement is a Data Definition Language (DDL) operation that is used to mark the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms intended to protect the data.

5. What is a JOIN in SQL? Can you explain different types of JOIN?

   JOIN is a means for combining columns from one (self-join) or more tables by using values common to each. ANSI-standard SQL specifies five types of JOIN: INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS.

6. What is the use of the DISTINCT keyword in SQL?

   DISTINCT keyword in SQL is used to return only distinct (unique) values in the result set. It eliminates all the duplicate records.

7. What are Indexes in SQL?

   Indexes are used to retrieve data from databases more quickly. Indexes are used on columns for faster search operations.

8. What is a View in SQL?

   A View is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

9. What is a Stored Procedure?

   A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again. It can take in parameters and can return a value.

10. What is a Trigger in SQL?

    A trigger in SQL is a special type of stored procedure that automatically runs when an event occurs in the database server.

Like with Python, these are just examples, and the actual questions you'll be asked can vary greatly depending on the specific role and company. Always study the job description to understand which concepts and skills are most important.

This appendix compiles common SQL interview questions, which touch on both basic and advanced aspects of SQL. They cover diverse topics, such as basic commands, joins, indexes, stored procedures, and more.

Let's get started:

1. What does SQL stand for, and what is it used for?

   SQL stands for Structured Query Language. It is a standard language used for interacting with relational databases. SQL can be used to insert, search, update, and delete database records. It can't write complete applications, but it allows you to manage data in databases.

2. What are the differences between SQL and NoSQL?

   SQL databases are relational, NoSQL are non-relational. SQL databases use structured query language and have a predefined schema. NoSQL databases have dynamic schemas for unstructured data.

3. Can you explain the basic types of SQL commands?

   SQL commands can be divided into five types based on their functionality: DDL (Data Definition Language), DML (Data Manipulation Language), DCL (Data Control Language), TCL (Transaction Control Language), and DQL (Data Query Language).

4. What is the difference between DELETE and TRUNCATE commands?

   DELETE is a DML command and TRUNCATE is a DDL command. DELETE statement is used to delete a row in a table. TRUNCATE statement is a Data Definition Language (DDL) operation that is used to mark the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms intended to protect the data.

5. What is a JOIN in SQL? Can you explain different types of JOIN?

   JOIN is a means for combining columns from one (self-join) or more tables by using values common to each. ANSI-standard SQL specifies five types of JOIN: INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS.

6. What is the use of the DISTINCT keyword in SQL?

   DISTINCT keyword in SQL is used to return only distinct (unique) values in the result set. It eliminates all the duplicate records.

7. What are Indexes in SQL?

   Indexes are used to retrieve data from databases more quickly. Indexes are used on columns for faster search operations.

8. What is a View in SQL?

   A View is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

9. What is a Stored Procedure?

   A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again. It can take in parameters and can return a value.

10. What is a Trigger in SQL?

    A trigger in SQL is a special type of stored procedure that automatically runs when an event occurs in the database server.

Like with Python, these are just examples, and the actual questions you'll be asked can vary greatly depending on the specific role and company. Always study the job description to understand which concepts and skills are most important.