With increasing employment opportunities in the database and digital job sector, the competitiveness for jobs also increases significantly.
Unfortunately, we have often seen that even highly skilled academics fail to snag a spot in the database management industry.
In contrast, less-skilled academics decipher the database management interview data and are selected. Well, that’s because of one thing, and it’s how well you prepare for the interview, how well you believe in yourself, and how well you know which type of SQL Interview Questions for data analyst must be designed.
It doesn’t matter whether you’re a newbie looking to start over in a programming career or an already working professional looking for an even better position in the industry; impressing interviewers with your knowledge and skills is the most crucial step you should take to get selected to work.
In this blog, we’ve got protected the utmost crucial SQL Interview Questions for Data Analyst that one must put together to assist him to electrify the interviewer and cracking the Data Analyst interview.
Data Analyst SQL Interview Questions and Answers for Beginner Level
Let us first start with the most asked SQL Interview Questions for data analyst that are generally asked to check their confidence and command on SQL.
Q1. Describe SQL.
SQL or Structured Query Language is a widely known programming language and is primarily used to interact with databases. SQL helps in operating different operations on databases such as extracting data, modifying data or updating data from the database. The programming language is used worldwide by a large number of companies to keep management of their various data, such as employee database, client database, etc.
Q2. What do you understand about Database?
Data organized in a way that is easy to access, retrieve, store and manage is a database. In simpler ways, a structured form of data is known as a database. Some command examples of databases are school management databases, employee management databases, and bank management databases.
Q3. Define Unique Key.
A constraint that uniquely defines every record in a given database is a Unique key. It is used to procure identity to a column or a set of columns.
There can be more than one Unique key constraint defined in a database table. However, only one primary key constraint can be defined in one table.
Q4. What do you understand about a Primary Key?
Assortment of fields uniquely defining a row is known as a Primary Key. A Primary key is a particular type of Unique key. Moreover, the Primary key of a table is a NOT NULL constraint, which means that the table’s primary key is never null.
Q5. What do you understand about a Foreign key and why it is used?
A key from one table that can relate to another table’s primary key is known as Foreign key. It is used to describe two different tables by refreshing the foreign key to the primary key of the other table.
Q6. Explain Normalization.
Fields and tables of a database are organized in order to minimise redundancy and dependency, this process is known as Normalization. Primarily, Normalization is used to delete, add or modify fields in a given table.
Q7. Give me a brief of DBMS, RDBMS and eventually MYSQL ?
For exact understanding of MYSQL , We need to understand some basic that’s DBMS and RDBMS .
DBMS stands for database management system , Which requires when we have a big amount of data which is supposed to be arranged systematically.
There are following Database management systems .
- Hierarchical
- Network
- Relational
- Object – Oriented.
Among them, MYSQL falls in the relational database management system. A system that stores data structured with rows and columns is a relational database management system. Thus it makes easy access to some specific data. It is “relational” because the values within each table are related to each other.
Q8. Explain database relationships and mention their various types
The connection between the tables in a database is known as Database Relationship. Database relationships are mainly of four types and are as follow:-
- One to One Relationship.
- One to Many Relationships.
- Many to One Relationship.
- Self-Referencing Relationship.
Q9. Tell me the difference between TRUNCATE and DELETE commands.
The TRUNCATE command is used to remove all the existing rows in a table at once and can not be rolled back once performed. On the other hand, the DELETE command is used to remove rows one by one or to remove a specific row and can be rolled back even after the command is performed.
Q10. Distinguish between global and local variables.
Global variables exist throughout the program and can be used anywhere in the program. Also one can not create the global variable when the function is called.
Local variables exist throughout the function and can be used anywhere in the function. One can call little variables whenever the function is called.
SQL Interview Questions for data analyst based on theoretical knowledge
It is highly recommended for a candidate to prepare for theoretical SQL Interview Questions for data analysts.
Q11. Define constraints and give five examples of them.
Limit on the data type of table is specified using a constraint. One can determine a constant while altering or even creating a table statement.
Five examples of contracts are:-
- CHECK.
- DEFAULT.
- UNIQUE.
- PRIMARY KEY.
- FOREIGN KEY.
Q12. Mention a major distinction among the Non-Cluster Index and Cluster Index?
A clustered index is used to clean and retrieve records from the database to change how the statistics are saved. Database types out rows with the aid of using the column which is ready to be clustered index.
A nonclustered index does not regulate how it changed into saved; however, it creates an entirely separate item on the desk. It factors lower back to the unique desk rows after searching.
Q13. What is Self-Join?
Self-join is ready to be query used to examine itself. This is used to examine values in a column with different values inside the identical column within the identical table. ALIAS ES is used for the identical table comparison.
Q14. What do you understand about user-defined functions?
User described or defined functions are the function written to apply the logic every time required. It isn’t always essential to write down the identical logic numerous times. Instead, the function may be referred to as or completed every time needed.
Q15. What is Cross-Join?
Cross-Join is a Cartesian product wherein a range of rows within the first table is extended through a range of rows within the second table. For instance, if the WHERE clause is utilized in costs-join, the question will function like an INNER JOIN.
Q16. Mention the various user-defined functions.
There are majorly three type of user defined functions and are as follow:-
- Scalar Functions.
- Inline Table valued Function.
- Multi declaration valued Function.
Q17. What is a Data Warehouse?
Datawarehouse is a critical repository of data from a couple of assets of information. That information is consolidated, converted, and made to be had for mining and online processing. In addition, warehouse data has a subset of information referred to as Data Marts.
Q18. What do you understand by Union, minus and Interact commands?
The UNION operator mixes the consequences of tables, and it gets rid of reproduction rows from the tables.
MINUS operator is used to going back rows from the primary query; however, not from the second query. Matching statistics of the 1st and 2nd query and different rows from the preceding query are displayed as a result set.
The INTERSECT operator is used to go back rows back to use each of the queries.
Q19. What is CLAUSE?
SQL clause is described to restrict the end result set with the aid of using offering conditions to the query. This typically filters a few rows from the entire set of records.
For instance, a query having WHERE condition or a query having HAVING condition.
Q20. Explain recursive stored procedure?
A stored procedure that calls using itself until it reaches a few boundary conditions is known as a Recursive stored procedure. This recursive technique or function allows programmers to apply the identical code set any wide variety of times.
Experienced Based SQL Interview Question for Data Analyst
Q21. Explain how you can restore the database in SQL Server?
First, Launch the SQL Server Management Studio and from the Object Explorer window interface, right-click on Databases and click on Restore. This action will routinely repair the database.
Q22. Tell me the difference between TRUNCATE and DROP statements?
TRUNCATE eliminates all of the rows from the table, and it can not be rolled back. DROP command eliminates a table from the database and operation can’t be rolled back.
Q23. What are scalar and aggregate functions?
An aggregate function is used to assess mathematical calculation and go back to solitary values. For example, this may be calculated from the columns in a table. Scalar function retreats an isolated value primarily based totally on the entered value.
Q24. What is the way of inserting data in a SQL server ?
The basic step is If the RDBMS is MYSQL, this is the way we insert date:
INSERT INTO tablename (col_name, col_date) VALUES (‘DATE: Manual Date’, ‘2021-9-21’)
Q25. How do I view tables in SQL ?
Show tables;
It is the only command used for viewing tables in SQL .
Q26. Explain DeNormalization.
The method used to enter data from higher to the lower normal form of the database is known as DeNormalization. We can bring up redundancy into a table by integrating data from the relative table by DeNormalization.
Q27. What is ETL in SQL ?
It’s a three-step process, i.e., Extract, Transformation, and load. First, we would extract data from sources that are collectively named Raw Data. The data is now transformed into a tidy form which is the second primary step. Finally, at last, we’ll load all these data to tools that help find insights.
Q28. How to install SQL?
The structural Query language is what SQL stands for, and it’s not something that can be installed. Instead, to experience SQL queries, one must need a relational database management system.
Q29. Explain the procedure to rename column names in SQL Server?
Using sp_rename is necessary to rename column names in SQL server because ALTER TABLE command is useless in SQL server.
Q30. What are Nested Triggers?
Triggers used for data modification is known nested triggers. Using DELETE statements, INSERT and UPDATE by DML can implement triggers.
SQL Interview Questions for data analyst based on SQL query
SQL interview questions for data analysts are always accompanied by questions based on SQL queries. One must learn all the important queries before his data analyst interview.
Q31. What will be the SQL query to get the number of employees working in project “A1”?
We can use the aggregate function count() with a SQL WHERE clause to receive the number of employees:-
SELECT COUNT(*)
FROM EmployeeSalary
WHERE Project = ‘A1’;
Q32. What will be the SQL query to procure the different projects available from the Employee-Salary table?
While relating to the Employee-Salary table, we can conclude that this table includes project values conforming to each employee, or it shows identical project values while assigning Project values from this table.
We can use distinct clause to perform the mentioned action:-
SELECT DISTINCT(Project)
FROM EmployeeSalary;
Q33. What will be an SQL query to procure mutual records between two tables?
This command can be performed by using an INTERSECT operator which will go as follow:-
SELECT * FROM EmployeeSalary
INTERSECT
SELECT * FROM ManagerSalary;
Q34. What will be the SQL query to procure records that are existing in one table but not in another table?
SQL command query to provide record is as follow:-
SQL Server – Using MINUS- operator-
SELECT * FROM EmployeeSalary
MINUS
SELECT * FROM ManagerSalary;
Q35. What will be the SQL query to upper case the name of the employee and lower case the city values in a given table?
One can utilise the SQL Upper and Lower function to procure the mentioned command:-
SELECT UPPER(FullName), LOWER(City)
FROM EmployeeDetails;
Q36. Write a query to get data of all the employees who are currently not working on any proposal.
(SQL queries are an important aspect SQL Interview Questions for data analyst and interviewer oftentimes ask questions from the NULL operator.)
This type of program command can be functioned by using the NULL operator.
SELECT EmpId
FROM EmployeeSalary
WHERE Project IS NULL;
Q37. What will be the SQL query to get all the Employees data from the EmployeeDetails table who enlisted in 2020?
SELECT * FROM EmployeeDetails
WHERE DateOfJoining BETWEEN ‘2020/01/01’
AND ‘2020/12/31’;
Q38. What will be the SQL query to procure the EmpIds that are existing in both the tables – ‘Table1’ and ‘Table2’?
The following query can be used to procure the asked data:-
SELECT EmpId FROM
Table1
where EmpId IN
(SELECT EmpId FROM Table2);
Q39. What will be the SQL query to get the employee full names and replace the space with ‘-’.
The mentioned task can be done by using the “Replace” function:-
SELECT REPLACE(FullName, ‘ ‘, ‘-‘)
FROM EmployeeDetails;
Q40. What query will you use to find the current date and time in MySQL, SQL Server and Oracle?
MySQL:-
SELECT NOW();
SQL Server:-
SELECT getdate();
Oracle:-
SELECT SYSDATE FROM DUAL;
Conclusion
It is significant for a man with great experience in the SQL work area to get properly ready and prepared for an SQL data analyst interview.
As you are reading this far, you must have learned some of the essential SQL interview questions for data analysts.
This understanding is beneficial for sure; however, you should also strive to analyze other SQL Interview Questions for data analyst as much as possible for more knowledge.
To crack an SQL data analyst interview, it is essential to be skillful and knowledgeable in every aspect of SQL and SQL interview questions for data analyst
