Mastering Table Joins with Pandas’ DataFrame

Shubham Soni
𝐀𝐈 𝐦𝐨𝐧𝐤𝐬.𝐢𝐨
4 min readJun 26, 2023
Tables Join

In the vast landscape of data manipulation, the ability to seamlessly combine and merge datasets is a coveted skill. As data professionals, we often find ourselves faced with the challenge of integrating information from various sources to extract valuable insights. This is where table joins come into play, and pandas’ DataFrame emerges as a formidable tool.

Joining tables is a fundamental operation in data analysis and database management. It allows us to combine data from multiple sources to gain comprehensive insights and make informed decisions. This is particularly relevant in various industries such as finance, e-commerce, healthcare, and government sectors, where data integration and analysis are crucial.

So, whether you are a data scientist, analyst, or enthusiast, let’s dive deep into the world of table joins with pandas’ DataFrame. Prepare to elevate your data manipulation prowess and unlock the full potential of your datasets.

Table joins in pandas allow you to combine data from multiple DataFrames based on a common column or index. Pandas provide different types of joins, including inner join, outer join, left join, and right join. Table joins in pandas allow you to combine data from multiple DataFrames based on a common column or index. Pandas provide different types of joins, including inner join, outer join, left join, and right join.

Temperature and Humidity Tables of cities.
import pandas as pd

df1 = pd.DataFrame({'city': ['Delhi', 'Mumbai', 'Chennai'], 'Temperature': [38, 32, 35]})
df2 = pd.DataFrame({'city': ['Mumbai', 'Delhi', 'Bangalore'], 'Humidity': [22, 48, 55]})

Inner Joins

An inner join returns only the matching records from both tables based on a common key. In Pandas, we can perform an inner join using the merge() function with the how=’inner’ parameter.

An inner join returns only the matching rows from both data frames based on the common column, which is ‘city’ in this case. Since ’Chennai’ and ’Bangalore’ are not present in both data frames, those rows will be excluded from the result.

pd.merge(df1,df2,on= 'city',how = 'inner')
Inner Joins

Outer Joins

An outer join returns all rows from both data frames, filling in missing values with NaN (null) if there is no match based on the common column.

pd.merge(df1,df2,on = 'city', how = 'outer')
Outer Joins

Left Joins

A left join returns all rows from the left data frame (df1) and the matching rows from the right data frame (df2). If there is no match, the missing values are filled with NaN.

pd.merge(df1,df2, on = 'city',how = 'left')
Left Joins

Right Joins

A right join returns all rows from the right data frame (df2) and the matching rows from the left data frame (df1). If there is no match, the missing values are filled with NaN.

pd.merge(df1,df2, on = 'city',how = 'right')
Right Joins

Table joins in data analysis and data science have several applications, including:

  1. Data Integration: Combining data from multiple sources to create a unified dataset for comprehensive analysis.
  2. Data Exploration and Analysis: Identifying relationships and patterns by merging relevant tables and uncovering insights across datasets.
  3. Data Preprocessing: Aligning and preparing data tables before analysis, handling missing data, and ensuring data quality.
  4. Customer Relationship Management (CRM): Consolidating customer data from various sources to gain a comprehensive view and improve customer management strategies.
  5. Machine Learning and Predictive Modeling: Merging tables to create feature-rich datasets for building predictive models that incorporate multiple factors.

Table joins are a crucial component of data analysis and data science. They enable data integration, exploration, and preprocessing, allowing analysts to combine and merge data from different sources. Table joins find applications in customer relationship management, machine learning, and predictive modeling. They facilitate comprehensive analysis, uncover insights, and support data-driven decision-making. In summary, table joins are fundamental tools for integrating, exploring, and analyzing data in various fields of data science and analysis.

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Shubham Soni
𝐀𝐈 𝐦𝐨𝐧𝐤𝐬.𝐢𝐨

A Data Scientist and Data Science, machine learning Instructor with years experience of build and solving complex architecture in diverse industries.