If you’re getting error 3581 in MySQL, which reads “A window which depends on another cannot define partitioning“, it’s probably because you’re using the PARTITION BY clause in a window function that refers to a named window.
To fix this issue, don’t use the PARTITION BY clause when referring to a named window.
When we have a query that returns a column with numerical data such as prices or population, we can use the following methods to automatically calculate the totals and subtotals within a category.
Continue readingMySQL provides us with a wide range of functions for working with JSON documents. Below are four MySQL functions that we can use to get information about JSON values.
Continue readingSQL provides us with an easy way to automatically compute the moving average of a given column.
The moving average (also known as the rolling average, running average, moving mean (MM), or rolling mean) is a series of averages of different selections of the full data set. The moving average changes as we move through the data set. We can add the moving average to our SQL query result sets to see how it changes across the result set.
Continue readingIf you’re getting error 3579 in MySQL, which reads something like “Window name ‘wf3’ is not defined“, it’s probably because you’re referring to a named window that doesn’t exist.
To fix this issue, make sure you refer to a named window that exists.
Continue readingWe can use SQL to create a running total of a given column. By this I mean, we can create a column that calculates the cumulative sum of a given column.
The running total/cumulative sum is the sum of all rows up until the current row. The result is that the sum increases (or decreases in the case of negative values) with each row returned in the result set. Each row’s value is added to the cumulative amount from all prior rows, so for any given row, we get the total sum for all rows up to that point – the “running total”.
Continue readingIf you’re getting error 3580 in MySQL, which reads “There is a circularity in the window dependency graph“, it’s probably because you’re using named windows that refer to each other in a way that creates a circular reference.
To fix this issue, make sure you don’t create a circular reference when referring to multiple named windows.
Continue readingIn SQL, we can use the following method to compute the number of items within a given range when using a window function.
By this I mean we can use a frame clause in the window function to output how many items have a value that’s in a similar range to the value in the current row.
Continue readingWhen we create or alter a CHECK constraint in MySQL, we have the option of setting it to ENFORCED or NOT ENFORCED. This determines whether or not MySQL will enforce the rules of the constraint whenever data that violates the constraint tries to enter the database.
We can use the ALTER TABLE statement to change the enforcement state of an existing CHECK constraint in MySQL, as shown in the following example.
If you’re getting MySQL error 1140, which reads something like “In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column ‘world.City.District’; this is incompatible with sql_mode=only_full_group_by“, it could be that you need to introduce a window function to the query.
This error can happen when we want multiple rows to contain aggregate values. For example, we might want to return subtotals of all rows within a group of rows. A window function can help us achieve this outcome.
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