In this post, we will discuss how to create a Cumulative Sum Column in MySQL where we can use any user-defined variable for keeping the track of the sum and continue to add on. And even we can use subquery and a join. And here we will discuss both ways to achieve our desired output as per our choice with some examples of the same.
Cumulative Values of Column
Here First we go with implementing the same using a user defined variable to keep a track of the sum and keep on adding the value each time in an additional column which we can insert just to implement.
SELECT id, value, @running_total := @running_total + value AS cum_sum FROM your_table CROSS JOIN (SELECT @running_total := 0) vars ORDER BY id;
Here we have taken the example that we are selecting three columns (id, Value, and sum) from a table called your table. We’re also initializing a user-defined variable called @running_total to zero using a Cross join with a subquery that sets the value of the variable. The @running_total: @running_total + value expression in the select list calculates the running total of the Value column by adding each value to the current value of @running_total The resulting cumulative sum is then stored in the sum column.
And another way to implement the same is given below just have a look to make it easier.
SELECT t1. id, t1. value, SUM(t2. value) AS cum_ sum FROM your_ table t1 JOIN your_ table t2 ON t2. id <= t1.id GROUP BY t1.id ORDER BY t1.id;
In the above given example, we are joining the ‘your table’ to itself using a less-than or equal-to comparison (t2. id <= t1. id) to include all rows up to and including the current row. We’re then grouping the results by the id column of the first instance of your table (t1. id) and using the sum() function to calculate the cumulative sum of the value column from the second instance of your table (v2.value). The resulting cumulative sum is stored in the cum sum column.
A few things we need to note here is that this method may be less efficient than using a user-defined variable, especially for large tables, since it needs a join operation and may generate a large intermediate result set. However, it can be a useful alternative if user-defined variables are not available or if you prefer to use a different syntax.
To Learn More about Creating a Sum Column in MySQL visit: by Java tutorial
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