SQL Interview Questions (2022) 

Conducting an interview can be challenging if you’re unprepared, but if you have the right questions, your interview will be much more successful. This list of SQL interview questions and answers provides you with 20 important questions that you should have on hand to help guide your conversation and help you determine whether or not this candidate is the right fit for your company. 

What is SQL? 

SQL stands for Structured Query Language. It is used to store, retrieve and manipulate data stored in a database management system. SQL was developed by IBM as part of their relational database management system called System R in 1979. The name SQL comes from Sequel. The first commercial implementation of SQL was in 1983 by Sybase Inc., which has been ported to most major database platforms. SQL became an ANSI standard in 1986 and today it is managed by Database Management Systems Working Group. SQL was originally designed for managing Relational DataBase Systems (RDS), but it can be used with other types of databases as well. SQL contains both data definition language (DDL) and data manipulation language (DML). DDL includes commands that create, modify or drop objects such as tables, views or indexes. DML includes commands that insert, update or delete rows from tables using values specified in a query statement. SQL Database also supports set-based operations through its use of GROUP BY clause which reduces processing time significantly over traditional row-by-row operations required by non-relational databases. 

What does SQL stand for? 

SQL stands for Structured Query Language. Invented by IBM in 1974, SQL is a standard language that allows users to access and manipulate data in relational databases. Today, SQL is used for all kinds of things from simple tables to complex documents and even XML files. Since it’s built into so many different applications, there are tons of different syntaxes and commands that can be used to perform a given task and knowing what kind of SQL code to use in any given situation can be daunting. That’s why we’ve put together our list of SQL interview questions! If you’re interviewing for a job as an SQL developer or database administrator, we recommend you take some time to familiarize yourself with these questions. They’ll help you understand how SQL works under-the-hood and give you an idea of what your interviewer will expect from you during your interview.  

How many types of queries can be run in T-SQL? 

T-SQL supports three types of queries: Data Definition Language (DDL), Data Manipulation Language (DML), and Stored Procedures. A DDL statement is used to create or modify schema objects, while a DML statement is used to query and update data in a table. For example, you can use an UPDATE statement to modify data within a table after it has been created. The CREATE PROCEDURE and CREATE FUNCTION statements are examples of stored procedures T-SQL statements that run in SQL Server. 

When do you use DML queries? 

If you don’t know what DML queries are, read about them in any introductory SQL textbook or online. There are two primary DML operations inserts and updates. Use an insert query when you want to add a record to a table. For example, if you want to add information about yourself to your Customer table, use an insert query. Use an update query when you want to modify or change data in an existing record. For example, if you just got a haircut and updated your Profile Picture on Facebook, you’d use an update query on that table in SQL Server. 

When do you use DCL queries? 

There are three common times you would use DCL queries: During your Data Definition Language Course, you were taught about DCL statements. These statements let you define and manipulate schema objects in SQL Server. The most common object to manipulate with DCL is your tables. However, some of these statements can also be used for other database objects such as views and indexes. Before creating any tables or columns in a database table, you would use DDL queries to ensure all of your SQL syntax is correct and consistent. 

By Cary Grant

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