Mysql AVG to ignore zero

I need to perform an avg on a column, but I know that most of the values in that column will be zero. Out of all possible rows, only two will pr开发者_如何学Cobably have positive values. How can I tell mySQL to ignore the zeros and only average the actual values?

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Assuming that you might want to not totally exclude such rows (perhaps they have values in other columns you want to aggregate)

SELECT AVG(NULLIF(field ,0)) 
from table

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You could probably control that via the WHERE clause:

select avg( field ) from table where field > 0

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select avg(your_column) 
from your_table 
where your_column != 0

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You can convert zeros to NULL, then AVG() function will work only with not NULL values.

UPDATE table SET column = NULL WHERE column='0';
SELECT AVG(column) FROM table;