如何在SQL查詢中添加第三個表格包含一個SUM

Question

我有以下SQL查詢：

SELECT porel.refcode, podetail.ponum, SUM(podetail.orderqty * podetail.unitcost) AS Total 
FROM podetail 
LEFT JOIN porel ON podetail.ponum = porel.ponum 
WHERE porel.poline=podetail.poline AND porel.reftype = 'SPEX' 
GROUP BY porel.refcode, podetail.ponum 
ORDER BY porel.refcode, podetail.ponum 

的正常工作帶給我他們對refcodes總值的ponums列表和。我現在要添加第三列vendor.name。 vendor表的字段vendorid與podetail表共享。

有多個podetail記錄與ponum相同，但這些也將匹配vendorid的。

有人可能會建議如何在vendor.name字段中添加而不返回額外的行嗎？

Answer 1

Heya，Rogue。我想說的比評論更適合，所以在這裏。

一個更容易診斷我的頭的頂部是這樣的：

SELECT 
    porel.refcode, 
    podetail.ponum, 
    SUM(podetail.orderqty * podetail.unitcost) AS Total, 
    podetail.vendorid 
FROM 
    podetail 
    LEFT JOIN porel 
    ON podetail.ponum = porel.ponum 
WHERE 
    porel.poline = podetail.poline 
    AND porel.reftype = 'SPEX' 
GROUP BY 
    porel.refcode, 
    podetail.ponum, 
    podetail.vendorid 
ORDER BY 
    refcode, 
    ponum 

在這裏，我們不加入到vendor可言，以表完全的方程。相反，我們只會捲起podetail.vendorid。

你可以發佈此查詢的輸出嗎？

Answer 2

將其添加到GROUP BY。我假設每個podetail.ponum都會有一個供應商。順便說一下，由於Where子句中的porel.reftype = 'SPEX'，當前的查詢將左連接轉換爲內連接。

SELECT porel.refcode, 
     podetail.ponum, 
     SUM(podetail.orderqty * podetail.unitcost) AS Total, 
     vendor.name 
FROM  podetail 
     INNER JOIN vendor ON podetail.vendorid = vendor.vendorid 
     LEFT JOIN porel ON podetail.ponum = porel.ponum 
WHERE porel.poline=podetail.poline 
AND  porel.reftype = 'SPEX' 
GROUP BY porel.refcode, 
     podetail.ponum, 
     vendor.name 
ORDER BY porel.refcode, 
     podetail.ponum 

Answer 3

SELECT porel.refcode, 
     podetail.poline, 
     podetail.ponum, 
     SUM(podetail.orderqty * podetail.unitcost) AS Total, 
     vendor.name 
FROM  podetail 
     INNER JOIN vendor ON podetail.vendorid = vendor.vendorid 
     LEFT JOIN porel ON podetail.ponum = porel.ponum 
WHERE porel.poline=podetail.poline 
AND  porel.reftype = 'SPEX' 
GROUP BY porel.refcode, 
     podetail.ponum, 
     vendor.name 
ORDER BY porel.refcode, 
     podetail.poline, 
     podetail.ponum 

我想，你缺少的需要包括podetail.poline在SELECT和GROUP BY。

Answer 4

既然你聚集podetails，只需骨料供應商名稱：

SELECT porel.refcode, podetail.ponum 
, MAX(vendor.name) as VendorName 
, SUM(podetail.orderqty * podetail.unitcost) AS Total 
FROM podetail 
LEFT JOIN vendor on podetail.vendorid = vendor.vendorid 
LEFT JOIN porel ON podetail.ponum = porel.ponum 
WHERE porel.poline=podetail.poline AND porel.reftype = 'SPEX' 
GROUP BY porel.refcode, podetail.ponum 
ORDER BY porel.refcode, podetail.ponum 

或使用MIN（），如果你喜歡。