Types of joins

Pandas Joins for Spreadsheet Users

John Miller

Principal Data Scientist

Three types of joins

  • Types

    • One-to-one
    • One-to-many
    • Many-to-many

  • Join type indicates relationship of tables

  • Like lookup values in VLOOKUP

data join cartoon

Pandas Joins for Spreadsheet Users

One-to-one

one to one join example

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  • Datasets at the same level
  • Lookup column same for both tables
  • Rows match one-to-one
Pandas Joins for Spreadsheet Users

One-to-many

one to many example

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  • Rows are unique at different levels
  • Join based on the higher-level column
  • Result based on lower-level column
  • Similar to VLOOKUP based on lower-level data
Pandas Joins for Spreadsheet Users

Many-to-many

many to many example

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  • Values are repeated
  • Results in all possible combinations
  • Can be hard to interpret
  • Best supplemented with a "bridge" table
Pandas Joins for Spreadsheet Users

Let's practice!

Pandas Joins for Spreadsheet Users

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