Crafting a Unique SQL Query to Eliminate Duplicate City Pairings

Learn how to create an SQL query that efficiently eliminates duplicate city pairings based on distance between cities, ensuring a cleaner dataset.
---
This video is based on the question https://stackoverflow.com/q/70810818/ asked by the user 'Rambo' ( https://stackoverflow.com/u/7149617/ ) and on the answer https://stackoverflow.com/a/70810879/ provided by the user 'Zakaria' ( https://stackoverflow.com/u/17645099/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: SQL query for below data input

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Crafting a Unique SQL Query to Eliminate Duplicate City Pairings

When working with city distance data, there's a common issue many data professionals encounter: duplicate entries for city pairs. For instance, you may find two records for the same cities with distances listed in reversed order. This can lead to a cluttered database and complicate data analysis. In this guide, we will discuss how to structure an SQL query to retrieve only unique pairings from a given set of data.

The Problem

Let's consider a simple dataset that captures distances between cities:

city1city2distanceRaipurGoa500GoaRaipur500ManikJamui200JamuiManik200NoidaPune100Here, the pairs "Raipur - Goa" and "Goa - Raipur" represent the same connection, as do "Manik - Jamui" and "Jamui - Manik." To keep things simple and clear, we want to output just one of each unique pair, along with their associated distance.

The Solution

The solution to filter out duplicates is to use SQL's DISTINCT, GREATEST, and LEAST functions effectively. Here’s a breakdown of how to accomplish this in SQL:

SQL Query Breakdown

We can set up our SQL query as follows:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Query

DISTINCT: This keyword is used to return only unique records and help eliminate duplicate rows in our result set.

GREATEST and LEAST:

GREATEST(city1, city2): This function returns the greater of the two cities in alphabetical order.

LEAST(city1, city2): This function returns the lesser of the two cities in alphabetical order.

By using GREATEST for city1 and LEAST for city2, we standardize how the cities are paired. No matter how the cities are ordered in your original data, this approach ensures they are consistently represented.

Expected Output

When executed, the SQL query will yield a cleaned-up output as follows:

city1city2distanceGoaRaipur500JamuiManik200NoidaPune100This shows each city pairing exactly once while preserving the distance value. The data is now more structured and easier for analysis or reporting purposes.

Conclusion

Effective data management and analysis often require cleaning up duplicates to maintain clarity and accuracy. Using the GREATEST and LEAST functions in SQL can help ensure that your datasets present unique entries without redundancy. This approach can greatly enhance data processing efficiency and reliability. If you run into similar issues with city pairings or any other duplicated data, remember to use this SQL solution as a reference!

By following this guide, you will be able to streamline your dataset without losing important information.

Видео Crafting a Unique SQL Query to Eliminate Duplicate City Pairings канала vlogize