一些我不知道如何写的SQL查询

Question

I need to create a few queries for a database with the following schema:

Patient(**pid**,pname,address,phone)
Ward(**wid**, wname) // wid=Ward id,
Bed(**wid,bid**) // bid=Bed id
Appointment(**apid**,date,result,pid,cid) // cid=Consultant id, pid=Patient id
Consultant(**cid**,cname,clinId,phone) // clinId=Clinic ID
Allocation(**apid**,pid,wid,bid,date,ex_leave,act_leave) //ex=expected, act=actual

The queries are:

1. Find how many unoccupied beds are in each ward.
2. Find the ward of which an allocation to it was made on every day during March 2013.
3. Return the consultant details of those who performed most appointments who led to allocation in the Orthopedic ward.

I tried to create the first one using views like this:

create view hospital.occupied_beds as
select A.wid,count(*) as o_beds
from hospital.allocation A,hospital.bed B 
where A.wid=B.wid and A.bid=B.bid and A.act_leave is null
group by A.wid;

create view hospital.all_beds as
select C.wid,count(*) as all_beds
from hospital.bed C
group by C.wid;

select distinct A.wid,all_beds-o_beds as uo_beds
from hospital.occupied_beds A, hospital.all_beds B

but this way it doesn't return wards in which all the beds are unoccupied.

Please help me :)

Answer 1

It seems a bit poorly normalized, in terms that Allocation can specify both ward ID and bed ID. Is bed ID nullable, eg the patient hasn't been allocated a bed yet?

In any case, I think you need outer joins. I don't have a copy of MySQL available right now, but I believe you can do this:

create view hospital.unoccupied_beds as
select B.wid,count(*) as o_beds
from hospital.allocation A right join hospital.bed B on A.wid=B.wid and A.bid=B.bid and A.act_leave is null
where A.apid is null
group by B.wid;

Answer 2

maybe something like this: you'll just need to calculate a litte bit:

Select Sub1.v1, Sub1.c1 as all, Sub2.c2 as free FROM
(SELECT wid.bed as v1,count(bid.bed) as c1 FROM bed, ward WHERE wid.ward =  wid.bed 
GROUP BY wid.bed) Sub1
LEFT JOIN
(SELECT wid.bed as v2,count(bid.bed) as c2 FROM bed, ward, allocation WHERE 
wid.ward =  wid.bed AND wid.bed = wid.allocation 
AND bid.bed = bid.allocation AND act_leave.allocation IS NULL GROUP BY wid.bed) Sub2
ON Sub1.v1 = Sub2.v2

Answer 3

Here are three possible solutions for your questions. Keep in mind that I was not going for efficiency. There are probably ways to optimize these queries a bit. I just wanted to give you ideas and get you going in the right direction.

For Unoccipied beds per ward:

select w.wname, bc.total - IFNULL(ob.occupied,0) as unoccupied
from Ward w,
(select wid, count(bid) as total from Bed group by wid) bc
left join (select wid, count(wid) as occupied from Allocation where act_leave is null   group by wid) ob
on bc.wid = ob.wid
where w.wid = bc.wid

For wards with allocations for every day in March 2013

select w.wid, w.wname, count(distinct(a.date)) as acount
from Ward w, Allocation a
where a.date >= '2013-03-01'
and a.date <= '2013-03-31'
and w.wid = a.wid
group by w.wid
having acount = 31

The list of consultants with most ortho appointments in descending order (most allocations on top)

select c.cid, c.cname, count(a.apid) as apptcount
from Consultant c, Appointment p, Allocation a, Ward w
where c.cid = p.cid
and p.apid = a.apid
and a.wid = w.wid
and w.wname = 'Orthopedic'
group by c.cid
order by apptcount desc