Question

我手头的任务是＆＃34;编写一个SQL语句来查找为每个分支中的每个屏幕安排的会话数。显示屏幕详细信息（分支和屏幕的ID）及其对应的会话数。使用branchid和会话数执行多级排序。＆＃34;

SELECT SCREENID, BRANCHID
FROM SCREEN NATURAL JOIN SESSIONS;

表格屏幕：

---------------------------------------
ScreenID | BranchID | Screencapacity
---------------------------------------
S1       | B1       | 120
S1       | B2       | 185
S2       | B1       | 230
S2       | B4       | 165
S2       | B3       | 185
S1       | B3       | 210
S2       | B4       | 170
S2       | B1       | 150
S3       | B2       | 135
S1       | B4       | 128
---------------------------------------

表会话：

+-----------+----------+----------+---------+-------------+--------------+
| SESSIONID | BRANCHID | SCREENID | MOVIEID | SESSIONDATE | SESSIONPRICE |
+-----------+----------+----------+---------+-------------+--------------+
| SS01      | B1       | S1       | M1      | 03-MAY-16   |         12.5 |
| SS03      | B1       | S2       | M2      | 03-MAY-16   |        12.67 |
| SS09      | B2       | S3       | M4      | 13-MAY-16   |         17.9 |
| SS04      | B4       | S2       | M4      | 13-MAY-16   |        14.56 |
| SS07      | B4       | S2       | M3      | 14-MAY-16   |        21.78 |
| SS05      | B3       | S2       | M5      | 23-MAY-16   |        14.56 |
| SS06      | B3       | S1       | M5      | 03-JUN-16   |        16.32 |
| SS02      | B2       | S1       | M2      | 04-JUN-16   |        19.45 |
| SS10      | B4       | S1       | M3      | 06-JUN-16   |        16.37 |
| SS08      | B1       | S2       | M2      | 06-JUN-16   |        16.82 |
+-----------+----------+----------+---------+-------------+--------------+

我完全迷失了，不知道从哪里开始这个问题

Answer 1

select screenid, branchid, count(1) as no_of_sessions
from screen A
    join session B
        on B.screenid = A.screenid
        and B.branchid = A.branchid
group by screenid, branchid
order by branchid, no_of_sessions
;

首先，您加入screenid和branchid上的两个表格。然后，您按group by和screenid将已加入的数据汇总（branchid）到组，并简单地计算每个组中的行数（count(1)）。然后，按branchid和结果中的会话数（no_of_sessions）对结果进行排序。

享受！

多级排序和显示详细信息

1 个答案: