Question

我有以下表格布局

ACCIDENTS包含事故ID
ACCIDENT_TO_CAR包含事故和车牌之间的关系 REPORT包含车牌和驱动程序名称

使用以下联接：

SELECT T_ACCIDENTS.ACCIDENT_ID,DRIVER_NAME
from T_ACCIDENTS
          inner join T_ACCIDENT_TO_CAR on T_ACCIDENT_TO_CAR.ACCIDENT_ID = T_ACCIDENTS.ACCIDENT_ID 
          inner join T_REPORT  on T_ACCIDENT_TO_CAR.PLATE = T_REPORT.PLATE 
and DRIVER_NAME in ('Foo','Moo')

目前司机'Foo'在报告中出现两次，因为他的两辆车出了车祸。

如何通过获取单个记录ACCIDENT_TO_CAR来限制加入驱动程序的结果所以换言之，基于驱动程序的报告是不同的

测试数据：

CREATE TABLE "T_ACCIDENTS" ("ACCIDENT_ID" VARCHAR2(20))

Insert into T_ACCIDENTS (ACCIDENT_ID) values ('1');
Insert into T_ACCIDENTS (ACCIDENT_ID) values ('2');
Insert into T_ACCIDENTS (ACCIDENT_ID) values ('3');



 CREATE TABLE "T_ACCIDENT_TO_CAR" 
   (    
   "PLATE" VARCHAR2(20 BYTE), 
    "ACCIDENT_ID" VARCHAR2(20 BYTE)
   ) 

Insert into T_ACCIDENT_TO_CAR (PLATE,ACCIDENT_ID) values ('1','1');
Insert into T_ACCIDENT_TO_CAR (PLATE,ACCIDENT_ID) values ('2','1');
Insert into T_ACCIDENT_TO_CAR (PLATE,ACCIDENT_ID) values ('4','2');
Insert into T_ACCIDENT_TO_CAR (PLATE,ACCIDENT_ID) values ('3','1');
Insert into T_ACCIDENT_TO_CAR (PLATE,ACCIDENT_ID) values ('2','2');



CREATE TABLE "T_REPORT" 
   (    
    "PLATE" VARCHAR2(20 BYTE), 
    "DRIVER_NAME" VARCHAR2(20 BYTE)
   )

Insert into T_REPORT (PLATE,DRIVER_NAME) values ('1','Foo');
Insert into T_REPORT (PLATE,DRIVER_NAME) values ('2','Foo');
Insert into T_REPORT (PLATE,DRIVER_NAME) values ('3','Moo');
Insert into T_REPORT (PLATE,DRIVER_NAME) values ('4','Bar');

UPDATE 对不起，数据集和查询不正确，我修好了！

Answer 1

使用DISTINCT关键字告诉Oracle仅包含唯一记录。

SELECT DISTINCT T_ACCIDENTS.ACCIDENT_ID,T_REPORT.DRIVER_NAME
from T_ACCIDENTS
          inner join T_ACCIDENT_TO_CAR on T_ACCIDENT_TO_CAR.ACCIDENT_ID = T_ACCIDENTS.ACCIDENT_ID 
          inner join T_REPORT  on T_ACCIDENT_TO_CAR.PLATE = T_REPORT.PLATE;

基于明确要求的更新

GROUP BY ACCIDENT_ID并按字母顺序选择名字的驱动程序。

SELECT T_ACCIDENTS.ACCIDENT_ID, MIN(DRIVER_NAME) DRIVER_NAME
from T_ACCIDENTS
          inner join T_ACCIDENT_TO_CAR on T_ACCIDENT_TO_CAR.ACCIDENT_ID = T_ACCIDENTS.ACCIDENT_ID 
          inner join T_REPORT  on T_ACCIDENT_TO_CAR.PLATE = T_REPORT.PLATE 
and DRIVER_NAME in ('Foo','Moo')
GROUP BY T_ACCIDENTS.ACCIDENT_ID;

Oracle内部联接 - 从右表中选择一行

1 个答案:

基于明确要求的更新