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…
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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…
ROW_NUMBER() Window Function – find duplicate values.
Many times, we do not want duplicate rows or values in our SQL tables. On the other hand, in some situations, it does not matter if there are duplicates present. For whatever reason, suppose duplicates have found their way into one of your tables. How can you find them quickly and easily? The ROW_NUMBER() Window function is a fantastic tool to use. Continue reading and see example queries you can apply to your own tables and find those duplicates…
MySQL Shell get_auto_increment_value() method – Python mode
These days, I mostly program in PHP with MySQL as the database, which is just fine by me. I have had a long-time interest in MySQL (SQL in general), and after several steady months of programming in PHP, I must say I have really come into the language and developed a fondness for it. All that being said, I still enjoy using and learning the MySQL Shell in Python mode. As Database Developers, we often need the LAST INSERT ID value from a previous INSERT statement on a column that has the AUTO_INCREMENT attribute. MySQL Shell has a get_auto_increment_value() method we can call against a Shell object result and retrieve that value. Continue reading and see examples of the MySQL Shell get_auto_increment_value() method used in Python mode…