테이블을 결합하는 동안 MySQL 잘못된 쿼리

Question

별도의 쿼리로 두 개의 테이블을 쿼리하고 있습니다. 그런 식으로하면 1 초 이내에 올바른 결과를 얻을 수 있지만, 병합을 시도하면 쿼리 (레코드가 많음)를 죽여야하기까지 정말 오래 걸립니다. 내가 뭘 잘못하고 있는지 궁금해.

원하는 출력

+--------+-----------+-----------+-----------+  
| name | computers | printers | tvs  | 
+--------+-----------+-----------+-----------+ 
| Peter | 12  | 1  | 5  | 
| Josh | 20  | 4  |   | 
| Bob | 15  | 4  | 9  | 
+--------+-----------+-----------+-----------+ 

검색어 1

SELECT 
    names.name, 
    SUM(IF(pcs.electronic = 'computers', 1,0)) AS computers, 
    SUM(IF(pcs.electronic = 'printers', 1,0)) AS printers 
FROM 
    electronics.pcs LEFT JOIN electronics.orders 
    ON pcs.id = orders.id 
    LEFT JOIN electronics.buying 
    ON orders.id = buying.id 
    LEFT JOIN dbnames.names names 
    ON names.clientid = pcs.clientid 
WHERE 
    pcs.clientid IS NOT NULL AND 
    pcs.belongs IN (10) 
GROUP BY pcs.clientid 

표 1 - 질의 1

+--------+-----------+-----------+ 
| name | computers | printers | 
+--------+-----------+-----------+ 
| Peter | 12  | 1  | 
| Josh | 20  | 4  | 
| Bob | 15  | 4  | 
+--------+-----------+-----------+ 

쿼리 2

SELECT 
    names.name, 
    SUM(IF(tvs.electronic = 'tvs', 1,0)) AS tvs 
FROM 
    electronics.tvs LEFT JOIN dbnames.names names 
    ON names.clientid = tvs.clientid 
WHERE 
    tvs.belongs IN (10) 
GROUP BY tvs.clientid 

표 2 - 쿼리 2

+--------+-----------+ 
| name | tvs  | 
+--------+-----------+ 
| Peter | 5  | 
| Bob | 9  | 
+--------+-----------+ 

Answer 1

이유는 간단 UNION하지? 그냥 생각

SELECT 
    names.name, 
    SUM(IF(pcs.electronic = 'computers', 1,0)) AS computers, 
    SUM(IF(pcs.electronic = 'printers', 1,0)) AS printers 
FROM 
    electronics.pcs LEFT JOIN electronics.orders 
    ON pcs.id = orders.id 
    LEFT JOIN electronics.buying 
    ON orders.id = buying.id 
    LEFT JOIN dbnames.names names 
    ON names.clientid = pcs.clientid 
WHERE 
    pcs.clientid IS NOT NULL AND 
    pcs.belongs IN (10) 
GROUP BY pcs.clientid 

UNION ALL 

SELECT 
    names.name, 
    SUM(IF(tvs.electronic = 'tvs', 1,0)) AS tvs 
FROM 
    electronics.tvs LEFT JOIN dbnames.names names 
    ON names.clientid = tvs.clientid 
WHERE 
    tvs.belongs IN (10) 
GROUP BY tvs.clientid 

...

Answer 2

멋지게 작동합니다 가입 가득하지만, MySQL은 지원하지 않기 때문에 전체 가입 .. 할 수 있습니다 UNION ALL 두와 해당 열에서 MAX을 사이 .

SELECT clientid, name, 
    MAX(computers) computers, 
    MAX(printers) printers, 
    MAX(tvs) tvs 
FROM 
(
    SELECT 
     pcs.clientid, 
     names.name, 
     SUM(IF(pcs.electronic = 'computers', 1,0)) AS computers, 
     SUM(IF(pcs.electronic = 'printers', 1,0)) AS printers, 
     NULL 
    FROM 
     electronics.pcs LEFT JOIN electronics.orders 
     ON pcs.id = orders.id 
     LEFT JOIN electronics.buying 
     ON orders.id = buying.id 
     LEFT JOIN dbnames.names names 
     ON names.clientid = pcs.clientid 
    WHERE 
     pcs.clientid IS NOT NULL AND 
     pcs.belongs IN (10) 
    GROUP BY pcs.clientid, names.name 
    UNION ALL 
    SELECT 
     tvs.clientid, 
     names.name, 
     NULL, NULL, 
     SUM(IF(tvs.electronic = 'tvs', 1,0)) AS tvs 
    FROM 
     electronics.tvs LEFT JOIN dbnames.names names 
     ON names.clientid = tvs.clientid 
    WHERE 
     tvs.belongs IN (10) 
    GROUP BY tvs.clientid, names.name 
) Q2 
GROUP BY clientid, name 

Answer 3

select * 
from 
(
    ... first query 
) as query1 
left join 
(
    ... second query 
) as query2 
on query1.name=query2.name;