Find Duplicates

Last modified: October 10, 2019

Contribute to Data School

We are actively working on this chapter. We are looking for two types of contributions:

  1. Help writing this chapter
  2. Share your story about working through this problem at work

Please reach out to @Matt David on our slack to discuss what you want to contribute.

Data School wants a comprehensive post with visuals to help people understand how to find duplicates in a table with SQL. Please use stack overflow to understand the many variations: https://stackoverflow.com/questions/2594829/finding-duplicate-values-in-a-sql-table

The structure of the post should be

  • Answer the question simply (provide sql query when appropriate)
  • Define example scenario we will be using (use a familiar dataset: facebook friends, Amazon store, Uber riders, etc)
    • Provide a small table
  • Use images to show what is happening
    • link to other Data School pages/images where appropriate (joins, aggregations, subqueries, window functions, case when)
  • Demonstrate in detail with SQL
  • Recap why this was important to answer the question

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