Question

每当我向下面的select语句添加一个计数时，它会导致它给我一个错误，我不确定原因：

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";

每当我运行它时，我都会收到以下错误：

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

我该怎么办？我正在使用Oracle数据库运行SQL命令行。

Answer 1

当您拥有count（或其他汇总功能）时，您需要group by非聚合项目

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"

顺便说一句，使用显式连接（除非您使用的是oracle的史前版本）而不是where子句

被认为是一种好习惯。

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

具有计数错误的多表查询

1 个答案: