SQL SUM值来自列并除以行数

Question

I'm trying to calculate a percentual...and I need to sum all values from a column (Its already ok) but I need divide the result by number of rows...

 select sum(voto) from tablename where id = numberHere

Answer 1

use COUNT to get the totalNumber of rows.

SELECT SUM(voto) / (COUNT(*) * 1.0) 
FROM   tablename 
WHERE  id = numberHere

by adding * 1.0 on the query will allow decimal places on the result.

or simply as

SELECT AVG(voto)
FROM   tablename 
WHERE  id = numberHere