How to Resample MySQL Database Values for Line Charts?

Resampling Database Values for Line Charts

When creating line charts with database values, it's often useful to reduce data resolution to improve performance and visibility. Selecting every nth row can achieve this resampling.

Question:

How can we select every 5th row from a MySQL database for creating a line chart?

Answer:

MySQL provides a method to resample data using the modulo operator and a row counter. The following query selects every 5th row:

SELECT * 
FROM ( 
    SELECT 
        @row := @row +1 AS rownum, [column name] 
    FROM ( 
        SELECT @row :=0) r, [table name] 
    ) ranked 
WHERE rownum % 5 = 1 

This query uses a nested SELECT statement to generate a temporary table with a row counter (@row). The outer SELECT statement then selects rows where the rownum is evenly divisible by 5.

By modifying the value in the WHERE clause, you can easily adjust the resampling frequency to suit your specific needs.

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