sql-server - 在 SQL 中连接多个表并获取 Count 数据

Question

我有三个表需要连接。我能够连接其中两个并获得所需的结果，并且此结果表需要与另一个表连接。

表1:

+----------+---------+------+
| Username | Country | Team |
+----------+---------+------+
| abc      | US      | New  |
| abc      | CAN     | New  |
| bcd      | US      | Old  |
+----------+---------+------+

表2:

+----------+-------------+----------+------------+
| Username | CompanyCode | Document | Entry Date |
+----------+-------------+----------+------------+
| abc      |           1 |      112 | 24/06/2014 |
| abc      |           2 |      123 | 24/06/2014 |
| bcd      |           3 |      456 | 24/06/2014 |
| efg      |           4 |      984 | 24/06/2014 |
+----------+-------------+----------+------------+

我编写了以下代码..

SELECT Username, CompanyCode, Document, IIF(MONTH([Entry Date]) = 6 AND YEAR([Entry Date]) = 2014, 'TRUE', 'FALSE') AS [Posted], 
       COALESCE(tNew.Country, 'not there') AS DC, COALESCE(tNew.Team, 'not there') AS Team FROM Table2
OUTER APPLY
    (
        SELECT TOP 1 Country, Team FROM Table1
        WHERE Table1.[Username] = Table2.[Username]
    ) tNew

...结果为 (Table99)...

+----------+--------------+----------+------------+--------+-----------+-----------+
| Username | Company Code | Document | Entry Date | Posted |  Country  |   Team    |
+----------+--------------+----------+------------+--------+-----------+-----------+
| abc      |            1 |      112 | 24/06/2014 | TRUE   | US        | New       |
| abc      |            2 |      123 | 24/06/2014 | TRUE   | US        | New       |
| bcd      |            3 |      456 | 24/06/2014 | TRUE   | US        | Old       |
| efg      |            4 |      984 | 24/06/2014 | TRUE   | not there | not there |
+----------+--------------+----------+------------+--------+-----------+-----------+

现在我有另一个表，Table3:

+--------------+--------------+
| Company Code | Company Name |
+--------------+--------------+
|            1 | MS           |
|            2 | APL          |
|            3 | GOO          |
|            4 | IBM          |
|            5 | AMZ          |
+--------------+--------------+

我想将 Company Code 上的 Table99 与 Table3 连接起来，并计算 Document WHERE Posted = TRUE AND Country <> 'not there' 的计数，结果...

+--------------+--------------+-----------------+
| Company Code | Company Name | Total Documents |
+--------------+--------------+-----------------+
|            1 | MS           |               1 |
|            2 | APL          |               1 |
|            3 | GOO          |               1 |
|            4 | IBM          |               0 |
|            5 | AMZ          |               0 |
+--------------+--------------+-----------------+

Answer 1

对 Table3 和原始查询执行 LEFT JOIN，然后使用条件 SUM 进行计数:

SELECT
    t3.CompanyCode,
    t3.CompanyName,
    SUM(CASE WHEN t.Posted = 'TRUE' AND t.Country <> 'not there' THEN 1 ELSE 0 END)
FROM Table3 t3
LEFT JOIN (
    SELECT 
        Username, 
        CompanyCode, 
        Document,
        tnew.Country, 
        IIF(MONTH(EntryDate) = 6 AND YEAR(EntryDate) = 2014, 'TRUE', 'FALSE') AS [Posted], 
        COALESCE(tNew.Country, 'not there') AS DC,
        COALESCE(tNew.Team, 'not there') AS Team
    FROM Table2
    OUTER APPLY(
        SELECT TOP 1 Country, Team FROM Table1
        WHERE Table1.[Username] = Table2.[Username]
    ) tNew
) t
    ON t3.CompanyCode = t.CompanyCode
GROUP BY t3.CompanyCode, t3.CompanyName
ORDER BY t3.CompanyCode

TRY IT HERE