如何对来自 table 的单个查询执行多个子查询？

Question

我有两个表：BUILDING 和 APARTMENT.

BUILDING 有 ID_BUILDING、BUILDING_NAME（这就是这个问题唯一重要的）

公寓有 ID_BUILDING、N_APARTMENTS、TOTAL_ROOMS。

我需要做这样的查询：

| BUILDING NAME | TOTAL APARTMENTS | TOTAL APARTMENTS WITH 1 BEDROOM | TOTAL APARTMENTS WITH 2 BEDROOMS |
|---------------|------------------|---------------------------------|----------------------------------|
| BUILDING A    | 31               | 8                               | 0                                 
|_______________________________________________________________________________________________________|
| BUILDING B    | 20               | 14                              | 11                               
|________________________________________________________________________________________________________
| BUILDING C    | 41               | 90                              | 5                                
|________________________________________________________________________________________________________

卧室的数量可以在 1 到 5 之间。

为此，我提出了 whis 查询：

SELECT E.BUILDING_NAME as "name", COUNT(D.N_APARTMENTS) "TOTAL APARTMENTS", (SELECT COUNT(D1.TOTAL_ROOMS) FROM APARTMENT D1 WHERE D1.TOTAL_ROOMS = 1)
FROM BUILDING E
JOIN APARTMENT D 
ON E.ID_BUILDING = D.ID_BUILDING    
GROUP BY E.E.BUILDING_NAME
ORDER BY E.BUILDING_NAME;

不幸的是，这计算了所有带 1 个房间的公寓，而不是 BUILDING_NAME:

| BUILDING NAME | TOTAL APARTMENTS | TOTAL APARTMENTS WITH 1 BEDROOM |
|---------------|------------------|---------------------------------|
| BUILDING A    | 31               | 122                             |
| BUILDING B    | 20               | 122                             |
| BUILDING C    | 41               | 122                             |

我确实尝试了 here and 的答案，但它们不是同一个问题。

我认为解决方案可能是使用多个连接（或内部连接），但我找不到正确的答案。

提前致谢。

Answer 1

使用条件聚合：

SELECT E.BUILDING_NAME as "name", 
 COUNT(D.N_APARTMENTS) "TOTAL APARTMENTS", 
 SUM(CASE WHEN D.TOTAL_ROOMS = 1 THEN 1 ELSE 0 END) AS "TOTAL APARTMENTS WITH 1 BEDROOM"
FROM BUILDING E
JOIN APARTMENT D 
ON E.ID_BUILDING = D.ID_BUILDING    
GROUP BY E.E.BUILDING_NAME
ORDER BY E.BUILDING_NAME;

如何对来自 table 的单个查询执行多个子查询？

How can I do multiples sub-querys on a single query from one table?

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