SQL 服务器 JOIN/APPLY 查询

Question

我应该使用什么连接来根据下面的虚拟 table 获得我想要的输出

详情TABLE

x------------------------------x
| empID | empName | date       |
x------------------------------x
| 1     | emp1    | 10/01/2016 |
| 1     | emp1    | 10/03/2016 |
| 1     | emp1    | 10/04/2016 |
| 1     | emp1    | 10/05/2016 |
| 1     | emp1    | 10/06/2016 |
x------------------------------x

列出日期从 10/01/2016 到 10/15/2016 OF TABLE

x------------x
| date       |
x------------x
| 10/01/2016 |
| 10/02/2016 |
| .......... |
| .......... |
| 10/15/2016 |
x------------x

我的查询所需的输出

x------------------------------x
| empID | empName | date       |
x------------------------------x
| 1     | emp1    | 10/01/2016 |
| null  | null    | 10/02/2016 |
| 1     | emp1    | 10/03/2016 |
| 1     | emp1    | 10/04/2016 |
| 1     | emp1    | 10/05/2016 |
| 1     | emp1    | 10/06/2016 |
| null  | null    | 10/07/2016 |
| null  | null    | 10/08/2016 |
| null  | null    | 10/09/2016 |
| null  | null    | 10/10/2016 |
| null  | null    | 10/11/2016 |
| null  | null    | 10/12/2016 |
| null  | null    | 10/13/2016 |
| null  | null    | 10/14/2016 |
| null  | null    | 10/15/2016 |
x------------------------------x

Answer 1

看来您只需要 outer join:

select e.empid, e.empname, d.date
from dates d 
   left join detail e on d.date = e.date

A Visual Explanation of SQL Joins

Answer 2

答案是 OUTER JOIN 它可以是 LEFT 或 RIGHT 取决于你在哪里使用 detail table。

SELECT D.empid, 
       D.empname, 
       LD.[date] 
FROM   detail D 
       RIGHT OUTER JOIN list_dates LD 
                     ON D.[date] = LD.[date]

您也可以使用 OUTER APPLY

SELECT D.empid, 
       D.empname, 
       LD.[date] 
FROM   list_dates LD 
       OUTER apply (SELECT * 
                    FROM   detail D 
                    WHERE  D.[date] = LD.[date]) D

SQL 服务器 JOIN/APPLY 查询

SQL Server JOIN/APPLY Query

sql

sql-server-2008

join

cross-apply

outer-apply