MySQL Window Function Compilation

If you use SQL on a regular basis, then you are well aware that Window Functions are powerful. They allow us to simplify queries that would otherwise be quite the mess. We can provide meaningful insight across rows of data without collapsing the results into a single value. I have written numerous blog posts on Window Functions, many here recently. I decided to make this blog post a compilation of all the Window Function posts I have written, providing a one-stop source for any readers interested in learning more about Window Functions…

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Top n Window Function queries in MySQL

Top n Window Function queries over a specific subset of data are common in analysis and reporting requirements. Luckily, in MySQL, there are Window functions we can use for this type of query. To be quite honest, you don’t necessarily need Window Functions. You can retrieve those top 3 (or whatever) types of results with a regular SQL query. But, since we have those powerful Window Functions, why not use them? My thoughts exactly! Besides, no one wants a spaghetti code mess of SQL to try and understand. Not to mention, Window functions are often better optimized for querying larger data sets. Continue reading and see example queries for more understanding…

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Rolling sum and average – Window Functions MySQL

Rolling sum and average query results are possible by combining the aggregate functions SUM() or AVG() with the OVER() clause, making for powerful analytic queries. I recently learned how to compute a rolling average or sum of values by using the Windowing option of the OVER() clause, applying the concepts to a data set I am familiar with. I wanted to share my learning with any readers who might be interested… [Keep reading for more SQL database and PHP/Python-centric content >>>]

RANK() and DENSE_RANK() differences

The Window Ranking functions: ROW_NUMBER(), RANK(), and DENSE_RANK() each rank rows with an increasing integer value. I wrote a previous blog post, ROW_NUMBER() Window Function – find duplicate values, where I covered how the ROW_NUMBER() window function can be used to target any duplicate rows, with the use of the PARTITION BY clause in the OVER() clause. In this post, I cover the differences between RANK(), and DENSE_RANK() in handling any ties according to the sorting performed by the ORDER BY clause with regards to the assigned increasing integer. Continue reading and see examples…

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Use MySQL UNIQUE Constraint in phpMyAdmin

The MySQL UNIQUE constraint is often used in a column definition in which we need each value for that column to be distinct from the others. Perhaps it is an email column for an on-line registration form and we want to ensure that users cannot register twice for an account using the same email. Whatever the case may be, UNIQUE is there to help us ensure this type of data integrity or business requirement. What if the target table already exists and you determine you need to add a UNIQUE constraint to an existing column? In this post, I will cover 2 ways you can implement a UNIQUE constraint on existing columns using the phpMyAdmin web interface…

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