Elentech Engineering Services Interview Questions and Answers

Group by is used to group data based on a common attribute. It can be used without a where clause.

• Group by is used to group data based on a common attribute

• It is used with aggregate functions like sum, count, avg, etc.

• It can be used without a where clause to group all the data in the table

• Group by is often used with having clause to filter the groups based on some condition

SQL is a programming language used for managing relational databases. It uses dynamic memory management.

• SQL stands for Structured Query Language

• It is used for managing and manipulating data in relational databases

• SQL uses dynamic memory management, which means that memory is allocated and deallocated as needed

• Examples of SQL-based relational database management systems include MySQL, Oracle, and Microsoft SQL Server

RDBMS is a relational database management system that organizes data into tables. SQL is used to query and manipulate data in RDBMS.

• RDBMS stands for Relational Database Management System

• It organizes data into tables with rows and columns

• SQL (Structured Query Language) is used to interact with RDBMS

• SQL allows querying, inserting, updating, and deleting data

• RDBMS and SQL provide a structured and efficient way to store and retrieve data

Aggregation functions are used to perform calculations on a set of values and return a single value as output.

• Aggregation functions are commonly used in databases and data analysis to summarize and analyze large amounts of data.

• Examples of aggregation functions include SUM, AVG, MAX, MIN, COUNT, and GROUP BY.

• These functions can be used to calculate totals, averages, maximum and minimum values, and counts of specific data points.

• Aggregation functions can also be used to group ...read more

To check which query is good, consider factors like execution time, resource usage, and accuracy of results.

• Check the execution time of the query and compare it with other queries.

• Analyze the resource usage of the query, such as CPU and memory usage.

• Check the accuracy of the results and compare them with the expected output.

• Consider the complexity of the query and its impact on the database.

• Take into account the scalability of the query and its ability to handle large dataset...read more

Python has several major libraries including NumPy, Pandas, Matplotlib, and Scikit-learn.

• NumPy is used for numerical computing and data analysis.

• Pandas is used for data manipulation and analysis.

• Matplotlib is used for data visualization.

• Scikit-learn is used for machine learning and data mining.