Display unmatched data along with aggregate functions and multiple joins - mysql

Question

So, what i have is a system using MySQL for storage that should be storing donations made by people (donators). Donation is entered into system by authorized user.
Here are create tables for all 4 tables:
CREATE TABLE `donator` (
`DONATOR_ID` int(11) NOT NULL AUTO_INCREMENT,
`DONATOR_NAME` varchar(50) NOT NULL,
`STATUS` char(1) COLLATE NOT NULL DEFAULT 'A',
PRIMARY KEY (`DONATOR_ID`)
)
CREATE TABLE `user` (
`USER_ID` int(11) NOT NULL AUTO_INCREMENT,
`USERNAME` varchar(100) NOT NULL,
`PASSWORD` varchar(200) NOT NULL,
`TYPE` char(1) COLLATE NOT NULL,
PRIMARY KEY (`USER_ID`)
)
CREATE TABLE `sif_res` (
`RES_ID` int(11) NOT NULL AUTO_INCREMENT,
`RES_NAME` varchar(50) NOT NULL,
`MON_VAL` double NOT NULL,
PRIMARY KEY (`RES_ID`)
)
CREATE TABLE `donations` (
`DONATION_ID` int(11) NOT NULL AUTO_INCREMENT,
`RESOURCE` int(11) NOT NULL,
`AMOUNT` int(11) NOT NULL,
`DONATOR` int(11) NOT NULL,
`ENTRY_DATE` datetime NOT NULL,
`ENTERED_BY_USER` int(11) NOT NULL,
PRIMARY KEY (`DONATION_ID``),
KEY `fk_resurs` (`RESOURCE``),
KEY `fk_donator` (`DONATOR``),
KEY `fk_user` (`ENTERED_BY_USER``),
CONSTRAINT `fk_1` FOREIGN KEY (`DONATOR`) REFERENCES `donator` (`DONATOR_ID`) ON UPDATE CASCADE,
CONSTRAINT `fk_2` FOREIGN KEY (`RESOURCE`) REFERENCES `sif_res` (`RES_ID`) ON UPDATE CASCADE,
CONSTRAINT `fk_3` FOREIGN KEY (`ENTERED_BY_USER`) REFERENCES `user` (`USER_ID`) ON UPDATE CASCADE
)
As you can see, I have a list of donators, users and resources that can be donated.
Now, I want to display all donators' name and their id's, however in third column I would like to display their balance (sum of all of items they donated) - this is calculated with
donation.AMOUNT * sif_res.MON_VAL
for each donation
The SQL SELECT I have written works, however donators that haven't donated anything are left out (they are not matched by JOIN). I would need that it displays everyone (with STATUS!=D) even if they don't have any entries (in that case their balance may be 0 or NULL)
This is my SQL i have written:
SELECT DONATOR_ID
, DONATOR_NAME
, round(SUM(d.AMOUNT * sr.MON_VAL)) as BALANCE
from donator c
join donations d on c.DONATOR_ID=d.DONATOR
join sif_res sr on sr.RES_ID=d.RESOURCE
where c.STATUS!='D'
group by DONATOR_ID, DONATOR_NAME
So, if i execute next sentences:
INSERT INTO donator(DONATOR_NAME, STATUS) VALUES("John", 'A'); //asigns id=1
INSERT INTO donator(DONATOR_NAME, STATUS) VALUES("Willie", 'A'); //asigns id=2
INSERT INTO user (USERNAME, PASSWORD, TYPE) VALUES("user", "pass", 'A'); //asigns id=1
INSERT INTO sif_res(RES_NAME, MON_VAL) VALUES("Flour", "0.5"); //asigns id=1
INSERT INTO donations(RESOURCE, AMOUNT, DONATOR, ENTRY_DATE, ENTERED_BY_USER) VALUES(1, 100, 1, '2.2.2017', 1);
I will get output (with my SELECT sentence above):
DONATOR_ID | DONATOR_NAME | BALANCE
--------------------------------------------
1 | John | 50
What i want to get is:
DONATOR_ID | DONATOR_NAME | BALANCE
--------------------------------------------
1 | John | 50
2 | Willie | 0
I have tried all version of joins (left, right, outer, full,..) however none of them worked for me (probably because i was using them wrong)
If it was just the problem of unmatched data i would be able to solve it, however the aggregate function SUM and another JOIN make it all more complicated

Answer 1

Using a left outer join on the second two tables should do the trick:
SELECT c.DONATOR_ID
, c.DONATOR_NAME
, ifnull(round(SUM(d.AMOUNT * sr.MON_VAL)),0) as BALANCE
from donator c
left outer join donations d on c.DONATOR_ID=d.DONATOR
left outer join sif_res sr on sr.RES_ID=d.RESOURCE
where c.STATUS!='D'
group by DONATOR_ID, DONATOR_NAME
I also wrapped the BALANCE expression in ifnull to display 0 instead of null.