Question

我有数据库，在其他表中我有一个：

CREATE TABLE `Physiotherapist`(
`pid` INT,
`name` VARCHAR(40),
`hours` INT,
`cid` INT

我想编写一个SQL查询，该查询返回一对在同一诊所工作但可以不返回重复项。到目前为止，我的答案是：

SELECT  p1.name AS name1, p2.name AS name2
FROM    Physiotherapist p1 
INNER JOIN Physiotherapist p2 on p2.cid = p1.cid AND p1.name != p2.name

或具有自我连接的替代解决方案：

SELECT  p1.name, p2.name
FROM    Physiotherapist p1, Physiotherapist p2
WHERE   p1.cid = p2.cid AND p1.name !=(SELECT p2.name)

无论哪种方式，我都会得到以下结果：

name1:            name2:

Jan Christensen   Ira Assent
Ira Assent        Jan Christensen

即同一对。我只需要一个重复项，因为它们显示相同的信息，但是我不知道一种方便的方法。

编辑：带有示例数据的完整数据库代码

DROP TABLE IF EXISTS Physiotherapist;

CREATE TABLE `Physiotherapist`(
    `pid` INT,
    `name` VARCHAR(40),
    `hours` INT,
    `cid` INT
);

INSERT INTO Physiotherapist VALUES('123','Ira Assent','8','1');
INSERT INTO Physiotherapist VALUES('246','Annika Schmidt','1','2');
INSERT INTO Physiotherapist VALUES('327','Jan Christensen','5','1');
INSERT INTO Physiotherapist(`pid`,`name`) VALUES('455','Simon Winter');

DROP TABLE IF EXISTS Clinic;

CREATE TABLE `Clinic`(
    `cid` INT,
    `name` VARCHAR(40),
    `address` VARCHAR(40)
);

INSERT INTO Clinic VALUES ('1','PhysCentral','Aarhus C');
INSERT INTO Clinic VALUES ('2','PhysIOgnomy','Aarhus N');
INSERT INTO Clinic VALUES ('3','Physios','Aarhus V');

DROP TABLE IF EXISTS Appointment;

CREATE TABLE `Appointment`(
    `aid` INT,
    `date` DATE,
    `time` INT,
    `pid` INT
);

INSERT INTO Appointment VALUES(34716,'2018-06-12','10','246');
INSERT INTO Appointment VALUES(23118,'2018-08-18','11','327');
INSERT INTO Appointment VALUES(88223,'2018-10-03','9','246');

Answer 1

还简单地包含pid <> pid（假设这是主键，从您的定义看来确实如此）

SELECT  p1.name AS name1, p2.name AS name2
FROM    Physiotherapist p1 
INNER JOIN Physiotherapist p2 
    on p2.cid = p1.cid 
    AND p1.name != p2.name 
    -- Add this to WHERE
    AND p1.pid != p2.pid

Answer 2

尝试

SELECT  p1.name, p2.name
FROM    Physiotherapist p1, Physiotherapist p2
WHERE   p1.cid = p2.cid AND p1.name !=(SELECT p2.name) AND p1.pid > p2.pid

这样，您应该只从两种可能的组合中获得一种。

Answer 3

我认为下面的查询将为您服务

select T3.* from 
(select clname,count( distinct pname) from
(SELECT  p1.name as pname,c.name as clname
FROM    Physiotherapist p1 inner join
 Clinic c on p1.cid=c.cid
 ) as T  GROUP BY clname
 having count( distinct pname)>1
) T2 inner join        

 (SELECT  p1.name as pname,c.name as clname
FROM    Physiotherapist p1 inner join
 Clinic c on p1.cid=c.cid
  ) t3 on t2.clname=t3.clname

http://sqlfiddle.com/#!9/1cbace/10

Answer 4

为了给您一个主意，我有一个带有authorid和bookid字段的出版物表。要获得至少一本书的共同作者，我的sql查询是：

SELECT p1.authorid , p2.authorid
FROM publications p1 , publications p2
WHERE p1.bookid = p2.bookid AND p1.authorid<>p2.authorid AND p1.authorid>p2.authorid;

希望你明白了

SQL-避免在自我联接/内部联接上出现重复对？

4 个答案: