How to Select Distinct Rows with Maximum Value in SQL

Learn how to use SQL to select distinct rows based on the maximum value of another column, ensuring data accuracy and relevance in your database queries.
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How to Select Distinct Rows with Maximum Value in SQL

Working with SQL databases often requires retrieving distinct rows from a table based on the maximum value of another column. This can be vital for data accuracy and ensuring relevant information in your query results. Here's how to accomplish this task effectively.

The Challenge

Suppose you have a table, example_table, with two columns, col1 and col2. Your task is to select distinct values of col1 while ensuring that for each distinct col1 value, you retrieve the row with the maximum value in col2.

The SQL Query

Achieving this can be efficiently done using a combination of GROUP BY, MAX(), and join or subquery techniques. The basic structure of the query is outlined below:

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

Step Breakdown:

Subquery to Find Maximum Value:

Filtering Rows:
The main query filters rows by comparing each col2 value with the maximum value obtained from the subquery. This ensures that for each distinct col1, only the row where col2 is the maximum is selected.

Advantages of This Approach

Accuracy: Ensures that you always get the most significant row for each col1 based on col2.

Efficiency: Using appropriate indexing, this query pattern can be optimized for performance.

Simplicity: The SQL query is straightforward and easy to understand, making it less prone to errors.

Conclusion

Selecting distinct rows in SQL based on the maximum values of another column is a common but essential task for maintaining data integrity and relevance. By following the query structure provided, you can ensure precise and efficient data retrieval.

Whether you're working with a simple dataset or managing extensive databases, mastering this SQL technique will undoubtedly improve your query results and overall data handling proficiency.