So I am currently in a DBMS class, and we are doing a section on SQL. It basically consists of me creating a database for 5 guests staying at a hotel. There are 8 tables with information (Tables listed below). I currently have all the info for the tables entered and working (not included below), but am stuck on a few queries that we are required to write for the assignment.
The query that I am stuck on: Don't even really know where to start on this one.
Name of guests who have incurred charges for golf and dinner in the
same itinerary.
Any help would be appreciated. I know I didn't include the actual data used for each table below, so let me know if you need any other information that may help to write the queries. Any help is appreciated, thanks.
1.GUEST (GUESTID, LASTNAME, FIRSTNAME, MIDINIT, STRADDR, CITY, STATE, ZIP, PHONE, EMAIL, AGE)
2.RESERVATION RESID, RESDATETIME, CHECKINDATE, CHECKOUTDATE, ROOMTYPE, TOTALCOST, GUESTID)
3.CREDITCARD (CCNO, TYPE, EXPIRYDATE, GUESTID)
4.ITINERARY (ITINID, CHECKINDATETIME, CHECKOUTDATETIME, ADULTCOUNT, CHILDCOUNT, GUESTID, ROOMNO)
5.ROOM (ROOMNO, ROOMTYPE, DAILYRATE, AMENITIES)
6.BILL (BILLID, BILLDATE, AMOUNTDUE, ITINID, CCNO)
7.CHARGETYPE (CHARGEID, DESCRIPTION)
8.CHARGES (CHARGEID, ITINID, CHARGEDATETIME, AMOUNT, GUESTID)
Because this is a homework assignment, I don't want to just post the answer, but I have good clues for you.
Question 1: You'll need to make an internal select statement (subquery) to determine the average charge across all charges before you can compare against each charge. Your subquery might look something like this:
SELECT AVG(AMOUNT) "AvgCharge" FROM CHARGES
You could put this in the SELECT portion of your statement or as a Cartesian product.
Question 2: I'm guessing you'll need to join the ITINERARY, CHARGES, and CHARGETYPE tables together. Here's a link for JOINs in Oracle. Afterwords, you'll have to limit that statement to only show golf and dinner charges.
Let's break it down. The first thing you need is the name of teh guest. Well clearly that has to come fromteh guest table.
so you have
select FIRSTNAME, MIDINIT, LASTNAME,
From Guest
Now you only want guests with Itineraries so you do an inner join to Itinerary (hint you join on GuestID)
select FIRSTNAME, MIDINIT, LASTNAME, ItineraryID
From Guest
JOIN ITINERARY on GUEST.GUESTID = ITINERARY.GUESTID
Now you only want guests who have charges for that ITINERARY.
So you would think to join to CHARGES and CHARGETYPE (to get the type of charges) and use a where clause to limit the charges to the types you are interested in. But becasue you want to make sure you have both types of charges, you need to join to CHARGES and CHARGETYPE twice (I don't know about Oracle but in SQL server these would need to be aliased (I would call them C1 and CT1 and C2 and CT2) I would suspect the same for Oracle). The first join will have a where clause of CT1 = 'dinner' and the second grouping of the two tables would include a where clause of CT2 = 'golf'
Related
I have two tables in my DB:
Building(bno,address,bname) - PK is bno. bno
Room(bno,rno,floor,maxstud) - PK is bno,rno (together)
The Building table stands for a building number, address and name.
The Room table stands for building number, room number, floor number and maximum amount of students who can live in the room.
The query I have to write:
Find a building who has at least 10 rooms, which the maximum amount of students who can live in is 1. The columns should be bno, bname, number of such rooms.
What I wrote:
select building.bno, building.bname, count(rno)
from room natural join building
where maxstud =1
group by bno, bname
having count(rno)>=10
What the solution I have states:
with temp as (
select bno, count(distinct rno) as sumrooms
from room
where maxstud=1
group by bno
)
select bno, bname, sumrooms
from building natural join temp
where sumrooms>=10
Is my solution correct? I didn't see a reason to use a sub-query, but now I'm afraid I was wrong.
Thanks,
Alan
Your query will perform faster but I'm afraid won't compile because you are not including every unaggregated column in the GROUP BY clause (here: building.bname).
Also, the solution that you have which isn't yours counts distinct room numbers, so one may conclude that a building can have several rooms with the same numbers for example on different floors, so that a room would be identified correctly by the unique triple (bno, rno, floor).
Given what I've wrote above your query would look:
select building.bno, building.bname, count(distinct rno)
from room natural join building
where maxstud = 1
group by 1,2 -- I used positions here, you can use names if you wish
having count(distinct rno) >= 10
Your solution is better.
If you are unsure, run both queries on a sample dataset and convince yourself that the results are the same.
I'm pretty much an Access n00b, but I've built a basic database for a friend's school to keep track of students seeing the counselling team. They're all pretty happy with it, but they've asked if it's possible to quickly see how many students each counselor is seeing.
I have tables set up for staff, students, and case notes, and I thought it would be easy to create a query that does this, but I cant get it to work; it keeps returning the number of case notes per staff member, rather than the students:
Query right now. Staff #7 has seen one student twice.
What I'd like it to do is tell me how many students each counselor is seeing, based on the case notes they've entered.
I'm really hoping for a solution I can implement in design view, rather than SQL.
You can DL the database if you want to look at it:https://drive.google.com/file/d/0B0RvbnEcKEagZldJMDZkZmkybkk/view?usp=sharing
(It's all dummy data)
Thanks in advance for any guidance you can offer me.
I was going to say, "count distinct," but apparently that's not a thing in Access.
Instead, you'll need to run two queries that are the equivalent of
select StaffID, FirstName, LastName, count(*)
from (
select distinct StaffID, FirstName, LastName, Student
from TblStaff stf join TblCaseNote nte on nte.Staff = stf.StaffID
) foo
group by StaffID, FirstName, LastName
The first query should have StaffID, FirstName, LastName, and Student, each set to Group By.
Then create another query that has the first as its source and Group By all columns except Student, which you should count.
Ok, so I have real difficulty with the following question.
Table 1: Schema for the bookworm database. Primary keys are underlined. There are some foreign key references to link the tables together; you can make use of these with natural joins.
For each publisher, show the publisher’s name and the average price per page of books published by the publisher. Average price per page here means the total price divided by the total number of pages for the set of books; it is not the average of (price/number of pages). Present the results sorted by average price per page in ascending order.
Author(aid, alastname, afirstname, acountry, aborn, adied).
Book(bid, btitle, pid, bdate, bpages, bprice).
City(cid, cname, cstate, ccountry).
Publisher(pid, pname).
Author_Book(aid, bid).
Publisher_City(pid, cid).
So far I have tried:
SELECT
pname,
bpages,
AVG(bprice)
FROM book NATURAL JOIN publisher
GROUP BY AVG(bpages) ASC;
and receive
ERROR: syntax error at or near "asc"
LINE 3: group by avg(bpages) asc;
You can't group by an aggregate, at least not like that. Also don't use natural join, it's bad habit to get into because most of the time you'll have to specify join conditions. It's one of those things you see in text books but almost never in real life.
OK with that out of the way, and this being homework so I don't want to just give you an answer without an explanation, aggregate functions (sum in this case) affect all values for a column within a group as limited by the where clause and join conditions, so unless your doing every row you have to specify what column contains the values you are grouping by. In this case our group is Publisher name, they want to know per publisher, what the price per page is. Lets work out a quick select statement for that:
select Pname as Publisher
, Sum(bpages) as PublishersTotalPages
, sum(bprice) as PublishersTotalPrice
, sum(bprice)/Sum(bpages) as PublishersPricePerPage
Next up we have to determine where to get the information and how the tables relate to eachother, we will use books as the base (though due to the nature of left or right joins it's less important than you think). We know there is a foreign key relation between the column PID in the book table and the column PID in the Publisher table:
From Book B
Join Publisher P on P.PID = B.PID
That's what is called an explicit join, we are explicitly stating equivalence between the two columns in the two tables (vs. implying equivalence if it's done in the where clause). This gives us a many to one relation ship, because each publisher has many books published. To see that just run the below:
select b.*, p.*
From Book B
Join Publisher P on P.PID = B.PID
Now we get to the part that seems to have stumped you, how to get the many to one relationship between books and the publishers down to one row per publisher and perform an aggregation (sum in this case) on the page count per book and price per book. The aggregation portion was already done in our selection section, so now we just have to state what column the values our group will come from, since they want to know a per publisher aggregate we'll use the publisher name to group on:
Group by Pname
Order by PublishersPricePerPage Asc
There is a little gotcha in that last part, publisherpriceperpage is a column alias for the formula sum(bprice)/Sum(bpages). Because order by is done after all other parts of the query it's unique in that we can use a column alias no other part of a query allows that, without nesting the original query. so now that you have patiently waded through my explanation, here is the final product:
select Pname as Publisher
, Sum(bpages) as PublishersTotalPages
, sum(bprice) as PublishersTotalPrice
, sum(bprice)/Sum(bpages) as PublishersPricePerPage
From Book B
Join Publisher P on P.PID = B.PID
Group by Pname
Order by PublishersPricePerPage Asc
Good luck and hope the explanation helped you get the concept.
You need ORDER BY clause and not GROUP BY to sort record. So change your query to:
SELECT pname, AVG(bprice)
FROM book NATURAL JOIN publisher
GROUP by pname
ORDER BY AVG(bpages) ASC;
You need Order By for sorting, which was missing:
SELECT
pname,
bpages,
AVG(bprice)
FROM book NATURAL JOIN publisher
GROUP BY pname, bpages
order by AVG(bpages) ASC;
Base on what you're trying to achieve. You can try my query below. I used the stated formula in a CASE statement to catch the error when a bprice is divided by zero(0). Also I added ORDER BY clause in your query and there's no need for the AVG aggregates.
SELECT
pname,
CASE WHEN SUM(bpages)=0 THEN '' ELSE SUM(bprice)/SUM(bpages) END price
FROM book NATURAL JOIN publisher
GROUP BY pname
ORDER BY pname ASC;
The ASC is part of the ORDER BY clause. You are missing the ORDER BY here.
Reference: http://www.tutorialspoint.com/sql/sql-group-by.htm
Check this
SELECT pname, AVG(bprice)
FROM book NATURAL JOIN publisher
GROUP by pname
ORDER BY AVG(bpages)
Say you have these tables:
PHARMACY(**___id_pharmacy___**, name, addr, tel)
PHARMACIST(**___Insurance_number___**, name, surname, qualification, **id_pharmacy**)
SELLS(**___id_pharmacy___**, **___name___**, price)
DRUG(**___Name___**, chem_formula, **id_druggistshop**)
DRUGGISTSHOP(**___id_druggistshop___**, name, address)
I think this will be more specific.
So, I'm trying to construct an SQL statement, in which I will fetch the data from id_pharmacy and name FROM PHARMACY, the insurance_number, name, and surname columns from PHARMACIST, for all the pharmacies that sell the drug called Kronol.
And that's basically it. I know I'm missing the relationships in the code I wrote previously.
Note: Those column names which have underscores left and right to them are underlined(Primary keys).
The query you've written won't work in any DBMS that I know of.
You'll most likely want to use some combination of JOINs.
Since the exact schema isn't provided, consider this pseudo code, but hopefully it will get you on the right track.
SELECT PH.Ph_Number, PH.Name, PHCL.Ins_Number, PHCL.Name, PHCL.Surname
FROM PH
INNER JOIN PHCL ON PHCL.PH_Number = PH.Ph_Number
INNER JOIN MLIST ON MLIST.PH_Number = PH.PH_Number
WHERE MLIST.Name = "Andy"
I've obviously assumed some relationships between tables that may or may not exist, but hopefully this will be pretty close. The UNION operator won't work because you're selecting different columns and a different number of columns from the various tables. This is the wrong approach all together for what you're trying to do. It's also worth mentioning that a LEFT JOIN may or may not be a better option for you, depending on the exact requirements you're trying to meet.
Ok, try this query:
SELECT A.id_pharmacy, A.name AS PharmacyName, B.Insurance_number,
B.name AS PharmacistName, B.surname AS PharmacistSurname
FROM PHARMACY A
LEFT JOIN PHARMACIST B
ON A.id_pharmacy = B.id_pharmacy
WHERE A.id_pharmacy IN (SELECT id_pharmacy FROM SELLS WHERE name = 'Kronol')
I'm taking a database course this semester, and we're learning SQL. I understand most simple queries, but I'm having some difficulty using the count aggregate function.
I'm supposed to relate an advertisement number to a property number to a branch number so that I can tally up the amount of advertisements by branch number and compute their cost. I set up what I think are two appropriate new views, but I'm clueless as to what to write for the select statement. Am I approaching this the correct way? I have a feeling I'm over complicating this bigtime...
with ad_prop(ad_no, property_no, overseen_by) as
(select a.ad_no, a.property_no, p.overseen_by
from advertisement as a, property as p
where a.property_no = p.property_no)
with prop_branch(property_no, overseen_by, allocated_to) as
(select p.property_no, p.overseen_by, s.allocated_to
from property as p, staff as s
where p.overseen_by = s.staff_no)
select distinct pb.allocated_to as branch_no, count( ??? ) * 100 as ad_cost
from prop_branch as pb, ad_prop as ap
where ap.property_no = pb.property_no
group by branch_no;
Any insight would be greatly appreciated!
You could simplify it like this:
advertisement
- ad_no
- property_no
property
- property_no
- overseen_by
staff
- staff_no
- allocated_to
SELECT s.allocated_to AS branch, COUNT(*) as num_ads, COUNT(*)*100 as ad_cost
FROM advertisement AS a
INNER JOIN property AS p ON a.property_no = p.property_no
INNER JOIN staff AS s ON p.overseen_by = s.staff_no
GROUP BY s.allocated_to;
Update: changed above to match your schema needs
You can condense your WITH clauses into a single statement. Then, the piece I think you are missing is that columns referenced in the column definition have to be aggregated if they aren't included in the GROUP BY clause. So you GROUP BY your distinct column then apply your aggregation and math in your column definitions.
SELECT
s.allocated_to AS branch_no
,COUNT(a.ad_no) AS ad_count
,(ad_count * 100) AS ad_cost
...
GROUP BY s.allocated_to
i can tell you that you are making it way too complicated. It should be a select statement with a couple of joins. You should re-read the chapter on joins or take a look at the following link
http://www.sql-tutorial.net/SQL-JOIN.asp
A join allows you to "combine" the data from two tables based on a common key between the two tables (you can chain more tables together with more joins). Once you have this "joined" table, you can pretend that it is really one table (aliases are used to indicate where that column came from). You understand how aggregates work on a single table right?
I'd prefer not to give you the answer so that you can actually learn :)