How to Include Null Months in Monthly Average Calculations?

Including Null Months in Monthly Average Calculations

This question seeks a solution for retrieving monthly averages while incorporating months with null values within a specified date range.

To address this, it is recommended to establish a separate table containing all possible months (dateTable). By connecting this table with the primary data table (myTable) through a LEFT JOIN, null values can be effectively captured.

Consider the following code:

<code class="sql">SELECT 
    `DT`.`myYear`, 
    `DT`.`myMonth`, 
    AVG(`myTable`.`value1`) AS `avg_value_1`, 
    AVG(`myTable`.`value2`) AS `avg_value_2`

FROM 
    `dateTable` AS `DT`

LEFT JOIN 
    `myTable`
ON 
    `dateTable`.`myDate` = `myTable`.`save_date`

WHERE 
    `dateTable`.`myDate` BETWEEN '2009-01-01' AND '2009-07-01'

GROUP BY 
    `DT`.`myYear`, `DT`.`myMonth`</code>

This approach allows for the grouping of results based on fields from the dateTable, enabling flexibility in reporting by financial quarter, month, day of week, and other relevant time-related factors.

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