如何獲得各個項目

-2

的計數，我有以下2個表分別命名爲ROOM和會話。如何獲得各個項目

ROOM 

BUILDINGNO | ROOMNO | ROOMCAPACITY 
-----------+--------+------------- 
B1   | R1  | 121 
B1   | R2  | 253 
B2   | R1  | 275 
B2   | R2  | 126 
B2   | R3  | 124 
B3   | R1  | 256  
B3   | R2  | 324 
B4   | R1  | 431 
B4   | R2  | 345 
B4   | R3  | 231 


SESSION 

SESSIONID | BUILDINGNO | ROOMNO | SPEAKERID 
----------+------------+--------+---------- 
SS01  | B1   | R1  | S1 
SS02  | B2   | R1  | S2 
SS03  | B1   | R2  | S2 
SS04  | B4   | R2  | S4 
SS05  | B3   | R2  | S5 
SS06  | B3   | R1  | S5 
SS07  | B4   | R2  | S3 
SS08  | B1   | R2  | S2 
SS09  | B2   | R3  | S4 
SS10  | B4   | R1  | S3

我希望能夠顯示位於每個房間的會話數量。理想情況下，會顯示一個這樣的表格。

BUILDINGNO | ROOMNO | NUMBEROFSESSIONS 
-----------+--------+----------------- 
B1   | R1  | 1 
B1   | R2  | 2 
B2   | R1  | 1 
B2   | R2  | 0 
B2   | R3  | 1 
B3   | R1  | 1 
B3   | R2  | 1 
B4   | R1  | 1 
B4   | R2  | 2 
B4   | R3  | 0

我知道我需要在某處使用COUNT和JOIN函數......但我至少有點卡住了。如果任何人都可以點我在正確的方向或解釋這對我來說將不勝感激:)

SELECT BUILDINGNUMBER, ROOMNO FROM ROOM ... COUNT? ... JOIN?

還有什麼可以讓我顯示/隱藏行，其中會話= 0的號碼嗎？

來源

2017-09-30 james

你的表數據不被標準化。 –

對不起，我或許應該補充約束ROOM_PK PRIMARY KEY（BUILDINGNO，ROOMNO） – james

@詹姆斯那不是正常化。 – Ravi

如果你只在每個房間內的會話數有興趣的話，我相信你有足夠的通知在SESSION表中。

SELECT BUILDINGNO, ROOMNO, COUNT(*)FROM SESSION 
GROUP BY BUILDINGNO, ROOMNO;

Here is a sql fiddle:

來源

2017-09-30 16:03:48 Thomas5631

你可以使用count（不同的SessionID）

SELECT ROOM.BUILDINGNO , ROOM.ROOMNO, count(distinct SESSION.sessionid) 
from ROOM 
left join SESSION on ROOM.ROOMNO = SESSION.ROOMNO 
    and ROOM.BUILDINGNO = SESSION.BUILDINGNO 
group by ROOM.BUILDINGNUMBER, ROOM.ROOMNO

和隱藏的房間與resul = 0，你可以使用具有

SELECT ROOM.BUILDINGNO , ROOM.ROOMNO, count(distinct SESSION.sessionid) 
from ROOM 
left join SESSION on ROOM.ROOMNO = SESSION.ROOMNO 
    and ROOM.BUILDINGNO = SESSION.BUILDINGNO 
group by ROOM.BUILDINGNUMBER, ROOM.ROOMNO 
HAVING count(distinct SESSION.sessionid) >0

，但你必須在表中的會話足夠的信息

SELECT SESSION.BUILDINGNO , SESSION.ROOMNO, count(distinct SESSION.sessionid) 
SESSION 
group by SESSION.BUILDINGNO , SESSION.ROOMNO 
HAVING count(distinct SESSION.sessionid) >0

來源

2017-09-30 15:43:00 scaisEdge

'SELECT ROOM.BUILDINGNO，ROOM.ROOMNO COUNT（DISTINCT SESSION.SESSIONID）從室溫LEFT加入會話 ON ROOM.ROOMNO = SESSION.ROOMNO AND ROOM.BUILDINGNO = SESSION.BUILDINGNO GROUP BY ROOM.BUILDINGNO，ROOM .ROOMNO;' 謝謝！ :)這給了我想要的。我將如何隱藏計數爲0的行？ – james

更好地解釋你對此有何評論..是不懂 – scaisEdge

可以使用具有..答案更新 – scaisEdge

SELECT r.BUILDINGNO, r.ROOMNO, count(1) QQ 
FROM ROOM r, SESS s 
WHERE 
r.ROOMNO = s.ROOMNO 
AND r.BUILDINGNO = s.BUILDINGNO 
GROUP BY r.BUILDINGNO, r.ROOMNO 
ORDER by r.BUILDINGNO;

[DEMO] [1] http://sqlfiddle.com/#!4/eb290/6

來源

2017-09-30 16:11:54 soft87

如何獲得各個項目

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