Complex SQL Interview Questions for Interview Preparation
For an SQL developer hoping to bag their dream job, mastering complex SQL queries is a must for cracking that SQL interview. In this competitive space, the importance of knowing the kind of complex SQL interview questions you can expect can’t be overstated. This article offers sample complex SQL interview questions to help you assess and direct your SQL interview preparation.
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In this article, we’ll learn:
- Complex SQL Interview Questions and Answers for Experienced Developers
- Complex SQL Interview Questions for Practice
- FAQs on Complex SQL Interview Questions
Complex SQL Interview Questions and Answers for Experienced Developers
Here are some sample complex SQL interview questions and answers to help you with your complex SQL preparation:
Q1. Write a query to get the last record from a table?
select * from Student where RowID = select max(RowID) from Student;
Q2. Write a query to get the first record from a table?
The first record can be fetched in two ways, one similar to the last record case, but with min:
select * from Student where RowID = select min(RowID) from Student;
The other method is by printing just one (first) row of the table:
select * from Student where Rownum = 1;
Q3. Write a query to display the first ten records from a table.
select * from Student where Rownum <= 10;
Q4. Create a table with the same structure with data as in the Student table.
Create table Student2 as Select * from Student;
Q5. Show only common records between two tables.
Select * from Student;
Select * from StudentA;
Want to know what SQL interview questions are asked at Facebook? Read this article.
Complex SQL Interview Questions for Practice
Now, check out these frequently asked complex SQL interview questions to gauge your interview preparation:
Complex PL SQL Server Interview Questions
These complex PL SQL server questions regularly feature at tech interviews for SQL developers:
- Define and describe the usage of a linked server.
- Name and explain the different types of Joins.
- Explain the different types of authentication modes.
- Which stored procedure would you run when adding a linked server?
- Where do you think the user names and passwords will be stored in the SQL server?
- How would you add email validation using only one query?
Check out this article for more basic and advanced PL SQL interview questions.
Complex SQL Queries Interview Questions
Interview questions related to complex SQL queries are quite common at interviews for developers. These involve questions like “what SQL query would you use to”:
- Fetch the number of Weekends in the current month
- Get the last 5 Records from the Student table
- Get the common records present in two different tables that have no joining conditions.
- Display records 5 to 9 from the Employee table.
- Display the last record of a table
- Display the third-last record of a table
- Convert seconds into time format
- Remove duplicate rows from a table
- Find the number of duplicate rows
- Find the fourth-highest score in the Students table using self-join
- Show the max and min salary together from the Employees table
- Display date in a DD-MM-YYYY table
- Create Employee_C table, which is the exact replica of the Employee table
- Drop all user tables from Oracle
- Calculate the number of rows in a table without using count
- Find repeated characters from your name
- Display department and month-wise maximum salary
- Find the second-highest salary in the Employee table.
- Select all the records from the Student table, where the names are either Anu or Dan.
- Select all the records from the Student table where the name is not Anu and Dan.
- Get Nth Record from the Student table.
- Get the 3 Highest salaries records from the Student table
- Show Odd rows in the Student table
- Show Even rows in the Student table
- Get the DDL of a table
- Get all the records from Employees who have joined in the year 2020.
- Find the maximum salary of each department.
- Find all Employees with their managers.
- Display the name of employees who joined in 2020 and have a salary is greater than 50000.
- Get the first 5 Records from the Student table.
- Get information of Employees where Employee is not assigned to any department.
- Show 1 to 100 Numbers
- Find duplicate rows in a table
- Get the previous month’s last day.
- Display a string vertically.
- The marks column in the Student table contains comma-separated values. How would you calculate the number of those comma-separated values?
- Get the 3rd highest salary using Rank Function.
- Create a table with its structure the same as the structure of the Student table.
- Display first 25% records from the Student table
- Display last 25% records from the Student table
- Create a table with the same structure and data as the Student table
- Get only the common records between two tables
- Get unique records from the table without using distinct keywords.
- Find the admission date of the Student in YYYY-DAY-Date format.
- Convert the System time into seconds.
- Display monthly Salary of Employee given annual salary.
- Get the first record from the Student table
- Get the last record from the Student table
To practice more SQL interview questions, read this article.
What do experts say?
Manish Devgan, CPO of the real-time data platform, Hazelcast, says, “Markets such as retail, e-commerce, and energy are seeing growing interest in applications where data has to be processed and analyzed in real-time. The use of SQL within streaming systems opens up a new chapter in the story of SQL within the data domain.”
FAQs on Complex SQL Interview Questions
Q1. What is a complex SQL query?
Complex SQL queries are parameter queries that go beyond the standard SQL usage of SELECT and WHERE and use two or more parameters. They also often heavily use AND and OR clauses. Complex queries are helpful because we can make more precise and accurate database searches with them.
Q2. How many types of SQL are there?
There are five types of SQL commands on the basis of the functionalities performed by them: DDL(Data Definition Language), DQL(Data Query Language), DCL(Data Control Language), DML(Data Manipulation Language) and TCL(Transaction Control Language).
Q3. Give a comparison between PostgreSQL and MongoDB.
PostgreSQL is a SQL database that uses tables with organized rows and columns for storing data. It is compatible with notions like JOINS and referential integrity entity-relationship. PostgreSQL uses SQL as the query language.
Q4. What is the difference between simple and complex views in SQL?
Simple views in SQL can contain only one base table. On the other hand, complex views in SQL have more than one base table. Complex views can also have a group by clause, join conditions, and order by clause.
Q5. What is a unique key in SQL?
The collection of data or columns in a table that allows us to recognize records distinctively is known as a unique key in SQL. The unique key ensures that the columns in the database are all unique. It is equivalent to the primary key; however, it may accept a null value compared to it.
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