多表查詢

每當我添加一個計數以下select語句，它會導致它給我的錯誤，我不知道爲什麼：多表查詢

select "WorkOrder"."WorkOrderID", "Vehicles"."Model", "Vehicles"."Color", 
"Vehicles"."LicensePlate", COUNT("WorkOrderPart"."WorkPartID") AS "Parts" 
FROM "WorkOrder", "Vehicles", "WorkOrderPart" 
WHERE "WorkOrder"."VIN" = "Vehicles"."VIN" AND 
"WorkOrder"."WorkOrderID" = "WorkOrderPart"."WorkOrderID";

每當我運行此，我得到以下錯誤：

select "WorkOrder"."WorkOrderID", "Vehicles"."Model", "Vehicles"."Color", 
     * 
ERROR at line 1: 
ORA-00937: not a single-group group function

我該怎麼辦？我正在用Oracle數據庫運行SQL命令行。

來源

2014-03-05 user3169698

當你有一個count（或其他聚合函數），你需要group by非聚集項

select 
    "WorkOrder"."WorkOrderID", 
    "Vehicles"."Model", 
    "Vehicles"."Color", 
    "Vehicles"."LicensePlate", 
    COUNT("WorkOrderPart"."WorkPartID") AS "Parts" 
FROM "WorkOrder", "Vehicles", "WorkOrderPart" 
WHERE "WorkOrder"."VIN" = "Vehicles"."VIN" 
AND "WorkOrder"."WorkOrderID" = "WorkOrderPart"."WorkOrderID" 
group by "WorkOrder"."WorkOrderID", "Vehicles"."Model", "Vehicles"."Color", 
"Vehicles"."LicensePlate"

順便說一句，它被認爲是很好的做法，使用顯式連接（除非你使用甲骨文的史前版本），而不是where條款

FROM "WorkOrder" 
    inner join "Vehicles" on "WorkOrder"."VIN" = "Vehicles"."VIN" 
    left join "WorkOrderPart" on "WorkOrder"."WorkOrderID" = "WorkOrderPart"."WorkOrderID"

來源

2014-03-05 20:23:17 podiluska

是的，與其他的功能太像'SUM'，'MIN'或'MAX' - 編輯：剛剛看到您的更新:) –

這並不工作，但，似乎我混淆了編輯自己。我的目標是爲WorkOrder表中的每個WorkOrderID生成一行，併爲Count COUNT計數返回0或更多。這隻返回1行。 – user3169698

您可能想要將工作順序和工作順序之間的「內部連接」更改爲「左連接」 - 請參閱上面的編輯 – podiluska

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