使用UNION刪除重複的行

Question

我試圖使用UNION獲取兩個具有相同字段的查詢。我需要的是重複的行被刪除，但它們不是。這兩個查詢都包含國家，Idcustomer，類型和成本。下面我舉一個例子：

Country | Idcustomer | Type | Cost        
Brazil  123   1  3,2 
Brazil  212   1  4,1 


Country | Idcustomer | Type | Cost 
Brazil  123   2  5,5 
Brazil  212   2  4,3 
Brazil  543   2  4,2 

提取後，我需要的是，如果Idcustomer是在兩個查詢，優先於第一個。我認爲聯盟會解決這個問題，因爲它會刪除重複的值，但不是。

Country | Idcustomer | Type | Cost 
Brazil  123   1  3,2 
Brazil  212   1  4,1 
Brazil  543   2  4,2 

任何想法？非常感謝！

SELECT A.* 
FROM (
    SELECT Country, Idcustomer, type, cost 
    FROM qry_cost 
    WHERE type = 1 
) AS A, 
    (
    SELECT qry_cost.Idcustomer, MIN(qry_cost.cost) AS cost_min 
    FROM qry_cost 
    WHERE type = 1 
    GROUP BY qry_cost.Idcustomer 
) AS B 
WHERE A.Idcustomer = B.Idcustomer 
    AND A.cost = B.cost 
UNION 
SELECT A.* 
FROM (
    SELECT Country, Idcustomer, type, cost 
    FROM qry_cost 
    WHERE type = 2 
) AS A, 
    (
    SELECT qry_cost.Idcustomer, MIN(qry_cost.cost) AS cost_min 
    FROM qry_cost 
    WHERE type = 2 
    GROUP BY qry_cost.Idcustomer 
) AS B 
WHERE A.Idcustomer = B.Idcustomer 
    AND A.cost = B.cost; 

Answer 1

 create table #Country1 
(
    country nvarchar(50), 
    idcustomer int, 
    type int, 
    cost decimal(19,6) 

) 
    create table #Country2 
    (
     country nvarchar(50), 
     idcustomer int, 
     type int, 
     cost decimal(19,6) 

    ) 
    create table #Country3 
    (
     country nvarchar(50), 
     idcustomer int, 
     type int, 
     cost decimal(19,6) 

    ) 


    insert into #Country1(country,idcustomer,type,cost) Values('Brazil', 123,1,3.2) 

    insert into #Country2(country,idcustomer,type,cost) VALUEs ('Brazil', 212,1,4.1) 

    insert into #Country3 (country,idcustomer,type,cost)VALUES ('Brazil', 123,2,5.5) 
    insert into #Country3(country,idcustomer,type,cost)VALUEs ('Brazil', 212,2,4.3) 
    insert into #Country3 (country,idcustomer,type,cost)VALUES ('Brazil', 543,2,4.2) 
-- YOUR ANSWER IS AS FOLLOWS  
    select * from #Country1 
    UNION 
    select * from #Country2 
    UNION 
    select * from #Country3 where cost= 4.2 


-- DROP IT  
    DROP TABLE #Country1 
    DROP TABLE #Country2 
    DROP TABLE #Country3 


--RESULT if you run ABOVE QUERY 

Reult

Answer 2

我認爲你需要確定哪些記錄保持在一個 「外」 查詢。所以，我的意思是將它全部包裝在一個新層中。例如：

SELECT * 
FROM (your entire query above) 
WHERE (your logic as to which records to keep)