多个表 select，子查询返回了超过 1 个值。 SQL

Question

我有两个表：

员工

id  | fullName   | birth      | speciality
1   | A A A      | 01/01/1980 | Manager
2   | B B B      | 01/01/1980 | Developer
3   | C C C      | 01/01/1980 | User

员工状况

ID  | status     | dateChange
1           | 1          | 01/01/2010
2           | 1          | 01/01/2013
3           | 1          | 01/01/2015
3           | 2          | 01/01/2016

我想选择以下数据

ID | Full name | Bith date | speciality | Date hired | Date fired

结果必须是：

ID | Full name    | Bith date   | speciality | Date hired | Date fired
1  | A A A        | 01/01/1980  | Manager    | 01/01/2010 | null
2  | B B B        | 01/01/1980  | Developer  | 01/01/2013 | null
3  | C C C        | 01/01/1980  | User       | 01/01/2015 | 01/01/2016
3  | C C C        |01/01/1980   | User       | 01/01/2017 | null

我的代码：

 SELECT Employees.id , Employees.fullName, Employees.birth, Employees.speciality,
(SELECT dateChange FROM EmployeesStatus WHERE status=1 AND id=Employees.id) datehired,
(SELECT dateChange FROM EmployeesStatus WHERE status=2 AND id=Employees.id) datefired FROM Employees

导致以下消息：

Msg 512, Level 16, State 1, Line 1 Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= ,

, >= or when the subquery is used as an expression.

有什么想法吗？

Answer 1

尝试以下操作：

SELECT E.ID,E.FULLNAME,E.BIRTH,E.SPECIALITY,ED.DATE_HIRED,ED.DATE_FIRED
FROM EMPLOYEES E,
(SELECT     ID,
        MAX(CASE WHEN STATUS=1 THEN DATECHANGE ELSE NULL END)DATE_HIRED,
        MAX(CASE WHEN STATUS=2 THEN DATECHANGE ELSE NULL END)DATE_FIRED
FROM EMPLOYEESSTATUS
GROUP BY ID)ED
WHERE E.ID=ED.ID

此查询在性能方面会更快，并且会得到相同的结果。

Answer 2

您应该使用基于子查询的联接而不是 =

SELECT 
    Employees.id 
  , Employees.fullName
  , Employees.birth
  , Employees.speciality
  , e1.dateChange as datehired, e2.dateChange as datefired
FROM Employees
INNER JOIN EmployeesStatus es1 on e1.status=1 AND e1.id=Employees.id
LEFT JOIN EmployeesStatus es2 on e2.status=2 AND e2.id=Employees.id

或者您可以在子查询中使用 in 子句而不是 =

Answer 3

除了@scaisEdge 回答：

SELECT 
    Employees.id,
    Employees.fullName,
    Employees.birth,
    Employees.speciality
    e1.dateChange as datehired, 
    MIN(e2.dateChange) as datefired
FROM Employees
INNER JOIN EmployeesStatus es1 on e1.status=1 AND e1.id=Employees.id
LEFT JOIN EmployeesStatus es2 on e2.status=2 AND e2.id=Employees.id
    AND e2.dateChange > e1.dateChange
GROUP BY Employees.id, 
    Employees.fullName,
    Employees.birth,
    Employees.speciality,
    e1.dateChange

Answer 4

试试这个

 SELECT e.id , 
        e.fullName,
        e.birth,
        e.speciality,   
        CASE WHEN t1.status = 1 then max(t1.dateChange) else null end as "Date Hired",
        CASE WHEN t2.status = 2 then max(t2.dateChange) else null end as "Date Fired",
    FROM Employees e
    LEFT JOIN EmployeesStatus t1 on t1.id = e.id and t1.status = 1
    LEFT JOIN EmployeesStatus t2 on t2.id = e.id and t1.status = 2

希望这有效..

多个表 select，子查询返回了超过 1 个值。 SQL

multiple tables select, Subquery returned more than 1 value. SQL

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