给出两个单独的SQL查询：
SELECT COUNT(N.NurseID) AS Nurses, D.DName, D.HName
FROM Department AS D, Nurse_Work AS N
WHERE N.DName = D.DName AND N.HName = D.HName
GROUP BY D.DName, D.HName;
SELECT COUNT(P.PhysicianID) AS Physicians, D.DName, D.HName
FROM Physician AS P, Department AS D
WHERE P.DName = D.DName AND P.HName = D.HName
GROUP BY D.DName, D.HName;
我得到以下结果：
SELECT COUNT(N.NurseID) AS Nurses, D.DName, D.HName FROM Department AS D,
Nurse_Work AS N WHERE N.DName = D.DName AND N.HName = D.HName GROUP BY
D.DName, D.HName
NURSES DNAME HNAME
----------- -------------------------------- ----------------------------------
8 General Surgery H1
10 General Surgery H3
7 General Surgery H4
10 General Surgery H5
7 General Surgery H2
3 Intensive Care Unit H1
2 Intensive Care Unit H3
1 Intensive Care Unit H4
2 Intensive Care Unit H5
3 Intensive Care Unit H2
6 Ophthalmology H1
4 Ophthalmology H3
4 Ophthalmology H4
2 Ophthalmology H5
2 Ophthalmology H2
3 Otolaryngology H1
1 Otolaryngology H3
2 Otolaryngology H4
2 Otolaryngology H5
2 Otolaryngology H2
4 Radiology H1
6 Radiology H3
4 Radiology H4
5 Radiology H5
6 Radiology H2
25 record(s) selected.
SELECT COUNT(P.PhysicianID) AS Physicians, D.DName, D.HName FROM Physician AS
P, Department AS D WHERE P.DName = D.DName AND P.HName = D.HName GROUP BY
D.DName, D.HName
PHYSICIANS DNAME HNAME
----------- ------------------------------------------------------------ ------------------------------------------------------------
2 General Surgery H1
2 General Surgery H3
2 General Surgery H4
2 General Surgery H5
2 General Surgery H2
1 Intensive Care Unit H1
1 Intensive Care Unit H3
1 Intensive Care Unit H4
1 Intensive Care Unit H5
1 Intensive Care Unit H2
1 Ophthalmology H1
1 Ophthalmology H3
1 Ophthalmology H4
1 Ophthalmology H5
1 Ophthalmology H2
1 Otolaryngology H1
1 Otolaryngology H3
1 Otolaryngology H4
1 Otolaryngology H5
1 Otolaryngology H2
1 Radiology H1
1 Radiology H3
1 Radiology H4
1 Radiology H5
1 Radiology H2
25 record(s) selected.
我的目标是找到员工人数最多的部门及其医院（护士和医生），我设法按工作分别计算出多少员工，现在我希望将结果表合并到一个表中左边是该部门/医院组合中护士和医生的总和。我尝试使用JOIN和UNION，但是它们似乎只给了我一个包含三列的结果表，其中一列同时显示了医生和护士以及分开的值而不是相加的值。如何创建一个带有一列的表，该表将汇总各个部门/医院组合的护士和医生人数？
答案 0 :(得分：3)
我将通过两个汇总查询（每个表一个）加入对部门详细信息的查询，然后添加两个计数：
SELECT d.dname,
d.hname,
COALESCE(num_nurses, 0),
COALESCE(num_physicians, 0),
COALESCE(num_nurses, 0) + COALESCE(num_physicians, 0) AS total
FROM department d
LEFT JOIN (SELECT dname, hname, COUNT(*) AS num_nurses
FROM nurse_work
GROUP BY dname, hname) n ON n.dname = d.dname AND n.hname = d.hname
LEFT JOIN (SELECT dname, hname, COUNT(*) AS num_physicians
FROM physician
GROUP BY dname, hname) p ON p.dname = d.dname AND p.hname = d.hname
答案 1 :(得分：0)
我使用了您的基本查询，并使用UNION ALL将其汇总在一起，因为如果医院中护士和医生的人数相同，则UNION可能会删除重复项，然后我将医生和护士的总和归纳。
Select DNAME,HName,SUM(CountAll) from
(SELECT COUNT(N.NurseID) AS CountAll, D.DName, D.HName
FROM Department AS D, Nurse_Work AS N
WHERE N.DName = D.DName AND N.HName = D.HName
GROUP BY D.DName, D.HName
UNION ALL
SELECT COUNT(P.PhysicianID) AS CountAll, D.DName, D.HName
FROM Physician AS P, Department AS D
WHERE P.DName = D.DName AND P.HName = D.HName
GROUP BY D.DName, D.HName)a
GROUP BY DNAME,HName