在加入时选择唯一字段

Question

CREATE TABLE Face.Person 
   ("LAST_NAME" VARCHAR2(50 BYTE), 
    "TICKET_NUMBER" VARCHAR2(50 BYTE));

insert into Person(last_name,ticket_number) values('johnson','100');
insert into Person(last_name,ticket_number) values('smith','200');

CREATE TABLE Face.Orders 
   ("REGION" VARCHAR2(50 BYTE), 
    "STATE" VARCHAR2(50 BYTE), 
    "A_CODE" VARCHAR2(5 BYTE),
    "STORE_NUM" VARCHAR2(50 BYTE), 
    "TICKET_NUMBER" VARCHAR2(50 BYTE),
    "SEQ" NUMBER(12));

insert into Orders(ticket_number, REGION, STATE, STORE_NUM, A_CODE, SEQ ) values('100', 'S', 'F1', '111', 'Mia', 1);
insert into Orders(ticket_number, REGION, STATE, STORE_NUM, A_CODE, SEQ ) values('100', 'S', 'F1', '222', 'FLL', 2);
insert into Orders(ticket_number, REGION, STATE, STORE_NUM, A_CODE, SEQ ) values('100', 'S', 'F1', '333', 'PBI', 3);
insert into Orders(ticket_number, REGION, STATE, STORE_NUM, A_CODE, SEQ ) values('100', 'S', 'F1', '444', 'BOC', 4);


SELECT A.LAST_NAME, A.TICKET_NUMBER, B.REGION, B.STATE 
FROM PERSON A
  JOIN Orders B ON A.TICKET_NUMBER 
    = (SELECT * FROM Orders WHERE A.TICKET_NUMBER= B.TICKET_NUMBER 
  AND ROWNUM = 1);

在票号上加入两个表。 Person 与 Orders 是一对多的关系。存在多个订单，但只需要一个与两个表中的票号匹配的订单记录（共 4 条）。原因是订单表中所需的字段对于具有相同票号的所有记录保持相同。

预期结果：

Johnson 100 S Fl 

person 表中的 Johnson 和 100 以及每个唯一票号的所有记录都保持相同的 S 和 FL 来自 Orders 表

甲骨文 12c

Answer 1

不清楚您从Orders 中选择记录的依据是什么。一种选择是简单地选择MIN() 的region 和state 与一组by 然后加入它Person

WITH b AS (
     SELECT ticket_number,
            MIN(region) AS region,
            MIN(state) AS state
     FROM orders
     GROUP BY ticket_number
) SELECT a.last_name,
         a.ticket_number,
         b.region,
         b.state
  FROM person a
  JOIN b ON a.ticket_number = b.ticket_number;

Demo