Get AVG ignoring Null or Zero values

Managing significant zero values

In situations where zeroes hold informational weight and should contribute to the average, one has to consider an alternative strategy. Ignoring zeroes could lead to a distorted outcome, reflecting a misguided business decision.

Power of sargable WHERE clause

Having a sargable WHERE condition is advantageous. Being sargable means the SQL Server can use indexes, if applicable. Without sargability, you can face full table scans that could degrade query performance, especially with large datasets.

Preserving data type precision with casting

To safeguard precision, casting could be necessary when dealing with various data types. For instance:

SELECT AVG(CAST(NULLIF(value, 0) AS DECIMAL(10,2))) 
FROM my_table
WHERE value IS NOT NULL;


This ensures the average is calculated using the DECIMAL data type with two decimal places of precision. No more, no less!

Avoiding unnecessary joins for simplicity

Simplicity is key in SQL queries. Especially with joining multiple tables, exclude the ones that aren't contributing to the desired AVG calculation:

-- Assuming join with another_table isn't needed for average calculation
SELECT AVG(NULLIF(my_table.value, 0))
FROM my_table;


Indeed, life's hard enough without needless complications.

Dealing with multiple columns

With multiple columns in play, apply the NULLIF function to each individual column inside the AVG function:

SELECT
  AVG(NULLIF(column1, 0)) AS avg_column1,
  AVG(NULLIF(column2, 0)) AS avg_column2
FROM my_table
WHERE column1 IS NOT NULL AND column2 IS NOT NULL;


Trust me, in SQL as in love, not everything should get equal attention!

The conditional magic with CASE

Garner more control with the CASE statement, as you can set multiple conditions on which values to include in the averaging operation:

SELECT AVG(CASE WHEN value > 0 THEN value END) 
FROM my_table;


This is where SQL starts to feel like "Choose Your Own Adventure."

The importance of testing

Always remember to test your queries to ensure the computation's correctness. Mistakes like syntactical errors or data structure misunderstandings can lead to surprising consequences.

Who knows, you might even discover DBA's dirty little secrets!

Timely data with specific time frame conditions

Specify the time period conditions to filter out irrelevant data:

SELECT AVG(NULLIF(value, 0)) 
FROM my_table
WHERE value IS NOT NULL 
AND date_column BETWEEN '2021-01-01' AND '2021-12-31';


Clear time frames, clear mind, can't lose.

Community support: you're not alone

Never hesitate to seek the community's assistance for complex calculations. We're all in this SQL journey together!

Reminder: Good old syntax check

A thorough check for syntax errors and typos can save time and frustration. Typos in your SQL, much like in your texts, can give a whole different meaning.