How to get SUM of f3 but Grouped by f2

I want to get all comments count grouped by category. eg

f1      f2      f3
php     hello   34
php     hello   34
php     hell开发者_如何转开发o   34
php     world   23
php     world   23
php     world   23
asp     world1   43
asp     world1  43
asp     world1   43

How to get sum of f3 but grouped by f2?

So not 34 + 34 + 34 +23 ... but 34 + 23 + 43

EDIT: f2 is unique

SELECT SUM(f3) FROM `tablename` GROUP BY f2, f3

Okay I thought it all over.. and basically if i do understand correct you want the sum for each distinct set.

So not 34 + 34 + 34 + 23 + 23 + 23 + 43 + 43 + 43 ... BUT 34 + 23 + 43

In order to that you need to trick MySQL with the following query :

SELECT 
SUM(tot.invalid_votes) AS total
FROM (SELECT DISTINCT QV, invalid_votes FROM `results`) tot

This will return the SUM of the Distinct values based on QV field.

Table :

QV  invalid_votes
0544    5
0544    5
0544    5
0545    6
0545    6

based on the database information you provided i get the following result 11

The only way I can think of to get the sum of the three different values is

Select sum (distinct f3) from yourtable

I hope it makes sense to you, because I'm still trying to figure out what you want.

Based on the pastebin you posted,

this should work

SELECT QV, SUM(invalid_votes) FROM `results` GROUP BY QV   

I get the following result

QV      SUM(invalid_votes)
0544    15
0545    12