複数のテーブルからのSQL SELECT

Question

customers1とcustomers2のすべての商品にどのように顧客名を含めることができますか？

customer1 table 
cid name1 
1 john 
2 joe 

customer2 table 
cid name2 
p1 sandy 
p2 linda 

product table 
pid cid pname 
1 1 phone 
2 2 pencil 
3 p1 pen 
4 p2 paper 

結果がはるかに優れています。この

pid cid pname name1 name2 
1 1 phone john NULL 
2 2 pencil joe NULL 
3 p1 pen NULL sandy 
4 p2 paper NULL linda 

Answer 1

SELECT p.pid, p.cid, p.pname, c1.name1, c2.name2 
FROM product p 
LEFT JOIN customer1 c1 ON p.cid = c1.cid 
LEFT JOIN customer2 c2 ON p.cid = c2.cid 

Answer 2

SELECT `product`.*, `customer1`.`name1`, `customer2`.`name2` 
FROM `product` 
LEFT JOIN `customer1` ON `product`.`cid` = `customer1`.`cid` 
LEFT JOIN `customer2` ON `product`.`cid` = `customer2`.`cid` 

Answer 3

SELECT pid, cid, pname, name1, name2 
FROM customer1 c1, product p 
WHERE p.cid=c1.cid 
UNION SELECT pid, cid, pname, name1, name2 
FROM customer2 c2, product p 
WHERE p.cid=c2.cid; 

Answer 4

select p.pid, p.cid, c1.name,c2.name 
from product p 
left outer join customer1 c1 on c1.cid=p.cid 
left outer join customer2 c2 on c2.cid=p.cid 

Answer 5

SELECT p.pid, p.cid, p.pname, c1.name1, c2.name2 
FROM product AS p 
    LEFT JOIN customer1 AS c1 
     ON p.cid = c1.cid 
    LEFT JOIN customer2 AS c2 
     ON p.cid = c2.cid 

Answer 6

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