14 SQL Data Analyst Interview Questions With Example Answers

In order to maintain consistency in a database, before and after the transaction, certain properties are followed. ACID (Atomicity, Consistency, Isolation, Durability) is a set of properties that guarantee that database transactions are processed reliably. For more details please read ACID properties in the DBMS article. It is true that SQL is a language, but it does not support programming as it is not a programming language, it is a command language. We do not have conditional statements in SQL like for loops or if..else, we only have commands which we can use to query, update, delete, etc. data in the database.

sql data analyst interview questions and answers

A trigger is a stored program in a database which automatically gives responses to an event of DML operations done by inserting, update, or delete. In other words, is nothing but an auditor of events happening across all database tables. Our database comprises of a lot of different entities such as tables, stored procedures, functions, database owners and so on. To make sense of how all these different entities interact, we would need the help of schema. So, you can consider schema to be the logical relationship between all the different entities which are present in the database.

Write a query to get the number of customers that were upsold by purchasing additional products.

Lag functions return data from a row that is preceding the current row, while lead functions return data from a row that is following the current row. A data scientist is responsible for extracting insights from data through the use of techniques such as machine learning and statistical modeling. Data scientists typically have a background in mathematics, statistics, and computer science, and are skilled at programming languages such as R and Python. Window functions allow us to use the RANK() or ROW_NUMBER() function to provide a numerical index based on a certain ordering. The LIKE operator is used to search for a specific pattern within a column.

  • DISTINCT is looking for unique combinations of row data for the columns you specify.
  • The ORDER BY clause in MySQL can be used without the ASC or DESC modifiers.
  • It also defines integrity constraints to enforce business rules on the data when it is entered into an application or a database.
  • To improve your ability to handle ambiguous data analytics take-home challenges like “Use SQL to find us some business insights in this dataset” my go-to resource is Lean Analytics.
  • As you prepare for your interview for Data Science roles, you should also start grasping the concepts of SQL to come out with flying colors.

This keyword is usually required whenever PRIMARY KEY in SQL is used. You can select unique records from a table by using the DISTINCT keyword. It is usually used in a GROUP BY clause and whenever GROUP BY is not used, HAVING behaves like a WHERE clause. Having Clause is only used with the https://wizardsdev.com/en/vacancy/sql-and-data-analyst-bi-analyst/ GROUP BY function in a query whereas WHERE Clause is applied to each row before they are a part of the GROUP BY function in a query. This statement allows conditional update or insertion of data into a table. It performs an UPDATE if a row exists, or an INSERT if the row does not exist.

Q6. What is the SELECT statement?

SQL Server is widely used for data analysis and also scaling up of data. SQL Server can be used in conjunction with Big Data tools such as Hadoop. In day-to-day activities, the user needs to find out the data between some range. To achieve this user needs to use Between..and operator or Greater than and less than the operator.

The retrieval happens through an SQL statement, incorporated into the view. So, you can think of a view object as a view into the base table. The view itself does not contain any real data; the data is electronically stored in the base table. PL/SQL is not a version of SQL, though, and that’s the tricky part of the question. PL/SQL is a complete procedural programming language and its scope of application is different. A Stored Procedure is a function which consists of many SQL statements to access the database system.

What is the use of mysql_close()?

So, if you have a SQL query that you create frequently, save it as a stored procedure and then call it to run it. You may also supply parameters to a stored procedure so that it can act based on the value(s) of the parameter(s) given. You may use the NVL function to replace null values with a default value. The function returns the value of the second parameter if the first parameter is null.

sql data analyst interview questions and answers

Databases, in general, hold collections of data that may be accessed and used in other applications. The development, administration, and use of database platforms are all supported by a database management system. Whereas, if we use a HAVING() clause, we filter data after our city average calculation and can perform a proper comparison with the national average.

What is the usage of NVL() function?

Here, we are copying the student table to another table with the same structure with no rows copied. A live lock is one where a request for an exclusive lock is repeatedly denied because a series of overlapping shared locks keep interferring. A live lock also occurs when read transactions create a table or page. The condition ensures that we extract only those records where the first name of the employee is ‘Steven’ and the second condition ensures that the salary of the employee is less than $10,000. In other words, we are extracting only those records, where the employee’s first name is ‘Steven’ and this person’s salary should be less than $10,000.

sql data analyst interview questions and answers

Data analyst roles have become extremely popular in recent times. Companies are aggressively hiring top talent in this largely data-driven world to process and leverage data better and build high-performing processes and systems. If you’re a data analyst preparing for technical interviews, you should be great with SQL. That’s because SQL interview questions for data analysts often feature in technical interviews for data engineering, data science, and database management roles. SQL is a standard database language used for accessing and manipulating data in databases. By executing queries SQL can create, update, delete, and retrieve data in databases like MySQL, Oracle, PostgreSQL, etc.

Can you discuss the process of feature selection and its importance in data analysis?

As a result, SQL creates a new table with a duplicate structure to accept the fetched entries, but nothing is stored into the new table since the WHERE clause is active. RDBMS is one of the most commonly used databases to date, and therefore SQL skills are indispensable in most of the job roles. In this SQL Interview Questions article, I will introduce you to the most frequently asked questions on SQL (Structured Query Language). This article is the perfect guide for you to learn all the concepts related to SQL, Oracle, MS SQL Server, and MySQL database.

We start off by giving the keywords CREATE PROCEDURE, then we go ahead and give the name of this stored procedure. After that, we give the AS keyword and follow it up with the SQL query, which we want as a stored procedure. Both the NVL(exp1, exp2) and NVL2(exp1, exp2, exp3) functions check the value exp1 to see if it is null. With the NVL(exp1, exp2) function, if exp1 is not null, then the value of exp1 is returned; otherwise, the value of exp2 is returned, but case to the same data type as that of exp1. With the NVL2(exp1, exp2, exp3) function, if exp1 is not null, then exp2 is returned; otherwise, the value of exp3 is returned. We can use the SELECT INTO statement to copy data from one table to another.


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