Question

我想从一些表中获得一些列。我的用户有问题。 userId可以为0，但我希望将其作为null返回。当我使用这个简单的union语句执行它时，结果如下所示：

SELECT 
      a.appointmentId, 
      u.prename AS user_prename, 
      u.lastname AS user_lastname, 
      a.start AS START , 
      a.end AS END , 
      w.workerId AS workerid 
FROM ios_appointments a 
     JOIN ios_user u
     JOIN ios_worker w 
     JOIN ios_partners p 
WHERE a.workerid_fk = w.workerid 
     AND w.partnerid_fk = p.partnerid 
     AND a.userid_fk = u.userid 
     AND p.code =  'DEMO6003' 
union 
select 
     a.appointmentId, 
     null, 
     null, 
     a.start AS START , 
     a.end AS END , 
     w.workerId AS workerid 
from ios_appointments a 
    JOIN ios_user u 
    JOIN ios_worker w 
    JOIN ios_partners p 
where 
    a.userid_fk = 0;

预期结果：

43  NULL    NULL    2013-01-10 02:00:00 2013-01-10 02:30:00 3

真实结果：

43  NULL    NULL    2013-01-10 02:00:00 2013-01-10 02:30:00 1
43  NULL    NULL    2013-01-10 02:00:00 2013-01-10 02:30:00 2
43  NULL    NULL    2013-01-10 02:00:00 2013-01-10 02:30:00 3

问题：该语句为在数据库中注册的每个worker返回一行。我该如何解决？

表架构：

CREATE TABLE `ios_workinghours` (
  `workingHourId` int(11) NOT NULL AUTO_INCREMENT,
  `start` time DEFAULT NULL,
  `end` time DEFAULT NULL,
  `workerid_fk` int(11) NOT NULL,
  PRIMARY KEY (`workingHourId`),
  KEY `workerid_fk` (`workerid_fk`)
)

create table ios_worker (
    workerid int not null auto_increment,
    prename varchar(255),
    lastname varchar(255),
    avatar varchar(255),
    lineup varchar(255),
    languages varchar(255),
    partnerid_fk int not null,
    primary key(workerid),
    foreign key(partnerid_fk) references ios_partners(partnerid)
)

create table ios_user (
    userid int not null auto_increment,
    prename varchar(255),
    lastname varchar(255),
    phone varchar(255),
    email varchar(255),
    password varchar(255),
    primary key (userid)
)

create table ios_partners (
    partnerid int not null auto_increment,
    code varchar(255),
    partnerName varchar(255),
    street varchar(255),
    zipCode varchar(255),
    city varchar(255),
    languages varchar(255),
    workers varchar(255),
    lineup varchar(255),
    primary key(partnerid)
)

Answer 1

您的第二个查询仍然需要应用加入条件：

FROM ios_appointments a 
     JOIN ios_user u
     JOIN ios_worker w 
     JOIN ios_partners p 
WHERE a.workerid_fk = w.workerid 
     AND w.partnerid_fk = p.partnerid 
     AND a.userid_fk = u.userid 
     AND a.userid_fk = 0

选择联合SQL语句的问题

1 个答案: