mysql sum with group by for different column value

2019-08-09 04:08发布

问题:

create table t (
  `place_id` int(11) NOT NULL ,
  `area_sq` int (11) NOT NULL,
  `nxx` int(11) NOT NULL
);
insert into t values(1, 50, 1);
insert into t values(2, 90, 2);
insert into t values(2, 20, 1);
insert into t values(2, 10, 0);
insert into t values(2, 10, 1);
insert into t values(3, 10, 3);


| PLACE_ID | AREA_SQ | NXX |
|----------|---------|-----|
|        1 |      50 |   1 |
|        2 |      90 |   2 |
|        2 |      20 |   1 |
|        2 |      10 |   0 |
|        2 |      10 |   1 |
|        3 |      10 |   3 |

above is my table called t. I need to get the following result

| PLACE_ID | SUM(AREA_SQ) |nxx |
|----------|--------------|----|
|        1 |           50 |   1|
|        2 |          100 |   2|
|        2 |           40 |   1|
|        3 |           10 |   3|

I want the sum of area_sq of same nxx plus sum of area_sq if nxx=0

my current query is like this. But I do not want sum of area_sq if nxx=0 as separate row, instead I want to add sum(area_sq) to others if nxx=0. So want to group by nxx as well but for nxx=0 area_sq should be added to the other nxx values. I am really sorry for incorrect English. I tried different things but none was successful. Thanks in advance.

select place_id,sum(area_sq) from t group by place_id,nxx

回答1:

You can have an extra subquery to be join which separately calculates the total sum of nxx = 0.

SELECT  t.PLACE_ID, 
        SUM(t.AREA_SQ) + COALESCE(s.AREA_SQ,0) totalSum, 
        NXX
FROM    t LEFT JOIN 
        (
            SELECT  PLACE_ID, SUM(AREA_SQ) AREA_SQ
            FROM    t 
            WHERE   NXX = 0
            GROUP   BY PLACE_ID
        ) s ON t.PLACE_ID = s.PLACE_ID
WHERE   NXX <> 0
GROUP   BY t.PLACE_ID, NXX
ORDER   BY t.PLACE_ID, totalSum DESC