將SQL查詢與當前查詢值進行比較

Question

如何將D1與D2進行比較並將結果用作查詢的一部分。

Select A.id, 
(Select b.date from b,c where b.id=c.id and c.id = E.id and b = 1) as D1, 
(Select b.date from b,c where b.id=c.id and c.id = E.id and b = 2) as D2 
from 
A,E 

我想用JOIN語法，而不是老式逗號拿到D1和D2

Select A.id, 
CASE 
WHEN D1 >= D2 
THEN D2 
WHEN D2 > D1 
THEN D1 
END 
FROM A,E 

Answer 1

退房的LEAST function：

SELECT id, LEAST(d1, d2) FROM (
    Select A.id, 
    (Select b.date from b,c where b.id=c.id and c.id = E.id and b.id = 1) as d1, 
    (Select b.date from b,c where b.id=c.id and c.id = E.id and b.id = 2)) as d2 
    from 
    A,E 
) 

Answer 2

使用sub-select

select id, 
     CASE WHEN D1 >= D2 THEN D2 ELSE D1 END 
From 
(
/* Your Query */ 
) A 

開始的下分開加入。這是正確的方式做到這一點

SELECT A.id, 
     D1, 
     D2, 
     Least(D1, D2) 
FROM A CROSS JOIN E 
     LEFT JOIN (SELECT Max(CASE WHEN b = 1 THEN date END) AS D1, 
         Max(CASE WHEN b = 2 THEN date END) AS D2, 
         E.Id 
        FROM b 
         INNER JOIN c 
           ON b.id = c.id 
        WHERE b IN (1, 2) 
        Group by E.Id) D 
       ON c.id = D.id 

Answer 3

我想你也許想是這樣的：

Select A.id, min(b.date) 
from A 
cross join b 
join c on b.id = c.id 
join E on c.id = E.id 
where b in (1,2) 
group by A.id