Here are the five top commonly asked SQL queries in the interviews. These you can expect in Data Analyst, or, Data Engineer interviews. Top SQL Queries for Interviews 01. Joins The commonly asked question pertains to providing two tables, determining the number of rows that will return on various join types, and the resultant. Table1 -------- id ---- 1 1 2 3 Table2 -------- id ---- 1 3 1 NULL Output ------- Inner join --------------- 5 rows will return The result will be: =============== 1  1 1   1 1   1 1    1 3    3 02. Substring and Concat Here, we need to write an SQL query to make the upper case of the first letter and the small case of the remaining letter. Table1 ------ ename ===== raJu venKat kRIshna Solution: ========== SELECT CONCAT(UPPER(SUBSTRING(name, 1, 1)), LOWER(SUBSTRING(name, 2))) AS capitalized_name FROM Table1; 03. Case statement SQL Query ========= SELECT Code1, Code2,      CASE         WHEN Code1 = 'A' AND Code2 = 'AA' THEN "A" | "A

SQL provides various constructs for calculating cumulative sums, offering flexibility and efficiency in data analysis. In this article, we explore three distinct SQL queries that facilitate the computation of cumulative sums. Each query leverages different SQL constructs to achieve the desired outcome, catering to diverse analytical needs and preferences. Using Window Functions (e.g., PostgreSQL, SQL Server, Oracle) SELECT id, value, SUM(value) OVER (ORDER BY id) AS cumulative_sum  FROM your_table; This query uses the SUM() window function with the OVER clause to calculate the cumulative sum of the value column ordered by the id column. Using Subqueries (e.g., MySQL, SQLite): SELECT t1.id, t1.value, SUM(t2.value) AS cumulative_sum FROM your_table t1 JOIN your_table t2 ON t1.id >= t2.id GROUP BY t1.id, t1.value ORDER BY t1.id; This query uses a self-join to calculate the cumulative sum. It joins the table with itself, matching rows where the id in the first table is greater than or

AWS (Amazon Web Services) and PySpark are separate technologies, but they can be used together for certain purposes. Let me provide you with a beginner's guide for both AWS and PySpark separately. AWS (Amazon Web Services): Amazon Web Services (AWS) is a cloud computing platform that offers a wide range of services for computing power, storage, databases, machine learning, analytics, and more. 1. Create an AWS Account: Go to the AWS homepage. Click on "Create an AWS Account" and follow the instructions. 2. Set Up AWS CLI: Install the AWS Command Line Interface (AWS CLI) on your local machine. Configure it with your AWS credentials using AWS configure. 3. Explore AWS Services: AWS provides a variety of services. Familiarize yourself with core services like EC2 (Elastic Compute Cloud), S3 (Simple Storage Service), and IAM (Identity and Access Management). PySpark: PySpark is the Python API for Apache Spark, a fast and general-purpose cluster computing system. It allows you

We will explore the world of data analysis using Python, covering topics such as data manipulation, visualization, machine learning, and more. Whether you are a beginner or an experienced data professional, join us on this journey as we dive into the exciting realm of Python analytics and unlock the power of data-driven insights. Let's harness Python's versatility and explore the endless possibilities it offers for extracting valuable information from datasets. Get ready to level up your data analysis skills and stay tuned for informative and practical content! Python Data Analyst Interview Questions 01: How do you import the pandas library in Python?  A: To import the pandas library in Python, you can use the following statement: import pandas as pd. Q2: What is the difference between a Series and a DataFrame in pandas?  A: A Series in pandas is a one-dimensional labeled array, while a DataFrame is a two-dimensional labeled data structure with columns of potentially different

Here are the best examples of Pandas fillna(), dropna() and sum() methods. We have explained the process in two steps - Counting and Replacing the Null values. Count Nulls ## count null values column-wise null_counts = df.isnull(). sum() print(null_counts) ``` Output: ``` Column1    1 Column2    1 Column3    5 dtype: int64 ``` In the above code, we first create a sample Pandas DataFrame `df` with some null values. Then, we use the `isnull()` function to create a DataFrame of the same shape as `df`, where each element is a boolean value indicating whether that element is null or not. Finally, we use the `sum()` function to count the number of null values in each column of the resulting DataFrame. The output shows the count of null values column-wise. to count null values column-wise: ``` df.isnull().sum() ``` ##Code snippet to count null values row-wise: ``` df.isnull().sum(axis=1) ``` In the above code, `df` is the Pandas DataFrame for which you want to count the null values. The `isnu

Here is Python logic that shows Parse and Read Different Files in Python. The formats are XML, JSON, CSV, Excel, Text, PDF, Zip files, Images, SQLlite, and Yaml. Python Reading Files import pandas as pd import json import xml.etree.ElementTree as ET from PIL import Image import pytesseract import PyPDF2 from zipfile import ZipFile import sqlite3 import yaml Reading Text Files # Read text file (.txt) def read_text_file(file_path):     with open(file_path, 'r') as file:         text = file.read()     return text Reading CSV Files # Read CSV file (.csv) def read_csv_file(file_path):     df = pd.read_csv(file_path)     return df Reading JSON Files # Read JSON file (.json) def read_json_file(file_path):     with open(file_path, 'r') as file:         json_data = json.load(file)     return json_data Reading Excel Files # Read Excel file (.xlsx, .xls) def read_excel_file(file_path):     df = pd.read_excel(file_path)     return df Reading PDF files # Read PDF file (.pdf) def rea

Pandas is a powerful data manipulation and analysis library in Python that provides a wide range of functions and tools to work with structured data. Whether you are a data scientist, analyst, or just a curious learner, Pandas can help you efficiently handle and analyze data.  In this blog post, we will walk through a step-by-step guide on how to start a Pandas project from scratch. By following these steps, you will be able to import data, explore and manipulate it, perform calculations and transformations, and save the results for further analysis. So let's dive into the world of Pandas and get started with your own project! Simple Pandas project Import the necessary libraries: import pandas as pd import numpy as np Read data from a file into a Pandas DataFrame: df = pd.read_csv('/path/to/file.csv') Explore and manipulate the data: View the first few rows of the DataFrame: print(df.head()) Access specific columns or rows in the DataFrame: print(df['column_name'])

 Creating a complex Python script is challenging, but I can provide you with a simplified example of a script that simulates a basic bank account system. In a real-world application, this would be much more elaborate, but here's a concise version. Python Complex Script Here is an example of a Python script that explains each step: class BankAccount:     def __init__(self, account_holder, initial_balance=0):         self.account_holder = account_holder         self.balance = initial_balance     def deposit(self, amount):         if amount > 0:             self.balance += amount             print(f"Deposited ${amount}. New balance: ${self.balance}")         else:             print("Invalid deposit amount.")     def withdraw(self, amount):         if 0 < amount <= self.balance:             self.balance -= amount             print(f"Withdrew ${amount}. New balance: ${self.balance}")         else:             print("Invalid withdrawal amount o

 Regular expressions (regex) are powerful tools for pattern matching and text manipulation in Python. Here are five Python regex examples with explanations: 01 Matching a Simple Pattern import re text = "Hello, World!" pattern = r"Hello" result = re.search(pattern, text) if result:     print("Pattern found:", result.group()) Output: Output: Pattern found: Hello This example searches for the pattern "Hello" in the text and prints it when found. 02 Matching Multiple Patterns import re text = "The quick brown fox jumps over the lazy dog." patterns = [r"fox", r"dog"] for pattern in patterns:     if re.search(pattern, text):         print(f"Pattern '{pattern}' found.") Output: Pattern 'fox' found. Pattern 'dog' found. It searches for both "fox" and "dog" patterns in the text and prints when they are found. 03 Matching Any Digit   import re text = "The price of the

Here are three awesome ways that you can use to remove duplicates in a list. These are helpful in resolving your data analytics solutions.  01. Using a Set Convert the list into a set , which automatically removes duplicates due to its unique element nature, and then convert the set back to a list. Solution: original_list = [2, 4, 6, 2, 8, 6, 10] unique_list = list(set(original_list)) 02. Using a Loop Iterate through the original list and append elements to a new list only if they haven't been added before. Solution: original_list = [2, 4, 6, 2, 8, 6, 10] unique_list = [] for item in original_list:     if item not in unique_list:         unique_list.append(item) 03. Using List Comprehension Create a new list using a list comprehension that includes only the elements not already present in the new list. Solution: original_list = [2, 4, 6, 2, 8, 6, 10] unique_list = [] [unique_list.append(item) for item in original_list if item not in unique_list] All three methods will result in uni

Here are ten Python projects along with code and possible solutions for your practice. 01. Palindrome Checker: Description: Write a function that checks if a given string is a palindrome (reads the same backward as forward). def is_palindrome(s):     s = s.lower().replace(" ", "")     return s == s[::-1] # Test the function print(is_palindrome("radar"))  # Output: True print(is_palindrome("hello"))  # Output: False 02. Word Frequency Counter: Description: Create a program that takes a text file as input and counts the frequency of each word in the file. def word_frequency(file_path):     with open(file_path, 'r') as file:         text = file.read().lower()         words = text.split()         word_count = {}         for word in words:             word_count[word] = word_count.get(word, 0) + 1     return word_count # Test the function file_path = 'sample.txt' word_count = word_frequency(file_path) print(word_count) 03. Guess the Nu

In Pandas, bfill and ffill are two important methods used for filling missing values in a DataFrame or Series by propagating the previous (forward fill) or next (backward fill) valid values respectively. These methods are particularly useful when dealing with time series data or other ordered data where missing values need to be filled based on the available adjacent values. ffill (forward fill): When you use the ffill method on a DataFrame or Series, it fills missing values with the previous non-null value in the same column. It propagates the last known value forward. This method is often used to carry forward the last observed value for a specific column, making it a good choice for time series data when the assumption is that the value doesn't change abruptly. Example: import pandas as pd data = {'A': [1, 2, None, 4, None, 6],         'B': [None, 'X', 'Y', None, 'Z', 'W']} df = pd.DataFrame(data) print(df) # Output: #      A     B

In PySpark, you can employ SQL queries by importing your CSV file data to a DataFrame. However, you might face problems when dealing with spaces in column names of the DataFrame. Fortunately, there is a solution available to resolve this issue. Reading CSV file to Dataframe Here is the PySpark code for reading CSV files and writing to a DataFrame. #initiate session spark = SparkSession.builder \ .appName("PySpark Tutorial") \ .getOrCreate() #Read CSV file to df dataframe data_path = '/content/Test1.csv' df = spark.read.csv(data_path, header=True, inferSchema=True) #Create a Temporary view for the DataFrame df2.createOrReplaceTempView("temp_table") #Read data from the temporary view spark.sql("select * from temp_table").show() Output --------+-----+---------------+---+ |Student| Year|Semester1|Semester2| | ID | | Marks | Marks | +----------+-----+---------------+ | si1 |year1|62.08| 62.4| | si1 |year2|75.94| 76.75| | si

 Pandas is a data analysis Python library.  The example shows you to convert a dictionary to a data frame. The point to note here is DataFrame will take only 2D data. So you need to supply 2D data.  Pandas Dictionary to Dataframe import pandas as pd import numpy as np data_dict = {'item1' : np.random.randn(4), 'item2' : np.random.randn(4)} df3=pd.DataFrame. from_dict (data_dict, orient='index') print(df3) Output 0 1 2 3 item1 -0.109300 -0.483624 0.375838 1.248651 item2 -0.274944 -0.857318 -1.203718 -0.061941 Explanation Using the NumPy package, created a dictionary with random values. There are two items - item 1 and item 2. The data_dict is input to the data frame. The from_dict method needs two parameters. These are data_dict and index. Here's the syntax you can refer to quickly. Related Hands-on Data Analysis Using Pandas How to create 3D data frame in Pandas

Here's a way without the Split function you can split (or extract) a substring. In Python the method is Partition. You'll find here how to use this method with an example.  How to Split the string using Partition method   Returns Left side part Example-1 my_string='ABCDEFGH||10||123456.25|' my_partition=my_string.partition('|')[0] print(my_partition) Output |10||123456.25| ** Process exited - Return Code: 0 ** Press Enter to exit terminal Example-2 Returns from the separator to last of the string. my_string='ABCDEFGH||10||123456.25|' my_partition=my_string.partition('|')[-1] print(my_partition) Output |10||123456.25| ** Process exited - Return Code: 0 ** Press Enter to exit terminal The use of Rpartition to split a string in Python Example-1 Returns except right side last separator. my_string='ABCDEFGH||10||123456.25|' my_partition=my_string.rpartition('|')[0] print(my_partition) Output ABCDEFGH||10||123456.25 ** Process exited -