SQL interview Questions & Answers is a must for any developer as all non-trivial applications need to talk to a database with CRUD operations. Q3 – Q15 are very popular with the interviewers. If you want to quickly practice your SQL skills try DB Fiddle or install MySQL locally as...
This continues 25+ SQL interview questions & answers – beginner
Q16. Why do you have CASE statements in SQL?
A16. CASE statements in SQL are similar to IF and ELSE conditions in programming languages. CASE statements are used to fetch particular values based on certain conditions.
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Setup the data on db-fiddle MySQL V8.0 to practice. This question is based on the LeetCode SQL problem Q. Given the below input: login table
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user_id date ----------------------- 1 2023-01-01 1 2023-01-02 1 2023-01-04 2 2023-01-01 2 2023-01-02 3 2023-01-09 4 2023-01-09 5 2023-01-12 6 2023-01-15 7 2023-01-18 |
txn table
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user_id date amount --------------------------------- 1 2023-01-01 75.00 1 2023-01-04 95.00 2 2023-01-02 60.00 3 2023-01-09 25.00 4 2023-01-09 25.00 5 2023-01-12 63.00 5 2023-01-12 74.00 5 2023-01-12 82.00 |
how will you write SQL query to output: 1) How many users who logged in did not do any transactions? …...
The below SQL problem can be practiced on MySQL database at db-fiddle or database of your choice. Use latest version from the drop down.
Q1. Given the below data, how will you get the individual sum of the count by score and cumulative sum over the whole data?
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Python Dataclasses interview Questions answered with examples. Dataclasses are python classes that are suitable for storing objects data.Python Dataclasses make your code less verbose. Q1. What are Dataclasses in Python? A1. The Python data classes were introduced from 3.7, … Read more ›...
The data analysts & engineers will often be faced with the below SQL scenario at work. It is also often asked in job interviews. This solution uses SQL analytical functions & you can learn more about them at SQL analytic functions interview questions – Part 1
Setup the data on db-fiddle MySQL V8.0 to practice.
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Q01. What is the difference between NumPy & Pandas? A01. Firstly, pandas, which is a Python library for data wrangling is built on top of the NumPy python library. NumPy is short for Numerical Python, and used for scientific computing. This library is made up of multidimensional array objects and...
This extends 50+ SQL scenarios based interview Q&As – identifying consecutive records – job status repetition. A popular SQL coding interview question. Setup the data on db-fiddle MySQL V8.0 to practice. Q. Given the below input, how will you list user_id & … Read more ›...
Q01. What is the difference between a Python List & NumPy? A01. Even though both superficially look the same with contents and indexes starting from 0 as shown below:
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import numpy as np # python list - index starts from 0 my_list = [1,2,3,4,5] # numpy array aka ndarray index starts from 0 my_numpy_array = np.array(my_list) |
NumPy arrays have a fixed size & homogeneous elements (i.e same type) at creation, … Read more ›...
Q01. What is a Non-Equi Join? A01. A Non-Equi Join in SQL that uses operators other than equality operator (i.e. ‘=’), like , = to join two tables. Q02. When to use a Non-Equi Join? … Read more ›...
Q01. What is an index in Pandas? A01. An index is a series of labels that can uniquely identify each row of a DataFrame. The index can be of any datatype like integer, string, hash, etc. pandas_test.py
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import pandas as pd sales = [['John', 'Notebook', 3], ['Peter', 'Mobile phone', 12], ['Sam', 'Camera', 3], ['David', 'Mobile phone', 9], ['Elliot', 'Notebook', 3], ['Elliot', 'Notebook', 3], ['John', 'Mobile phone', 13], ['Peter', 'Mobile phone', 2] ] columns = ['emp_name', 'product', 'qty'] #row indexes idx = [101, 102, 103, 104, 105, 106, 107, 108] # pandas Dataframe data = pd.DataFrame(sales, columns=columns, index=idx) print(data) |
Run as:
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$ python3 pandas_test.py |
Outputs:
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emp_name product qty 101 John Notebook 3 102 Peter Mobile phone 12 103 Sam Camera 3 104 David Mobile phone 9 105 Elliot Notebook 3 106 Elliot Notebook 3 107 John Mobile phone 13 108 Peter Mobile phone 2 |
Q02. … Read more ›...
Why learn Scala? and where to use Scala? are very popular questions in forums like LinkedIn, Quora, Stack Overflow, etc. Here is my take on learning Scala with 3 reasons.
#1. I am already proficient in Java
Learning new programming languages (e.g. Scala) and paradigms (e.g.
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This post covers SQL examples to perform quality checks, clean data and profile data. Q01. What is Data Cleaning? Can SQL do data cleaning? A01. Data cleaning is the process of fixing bad data. … Read more ›...
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