I am practicing a bit with SQL and I came across this exercise:
Consider the following database relating to albums, singers and sales:
Album (Code, Singer, Title)
Sales (Album, Year, CopiesSold)
with a constraint of referential integrity between the Sales Album attribute and the key of the
Album report.
Formulate the following query in SQL :
Find the code and title of the albums that have sold 10,000 copies
every year since they came out.
I had thought of solving it like this:
SELECT CODE, TITLE, COUNT (*)
FROM ALBUM JOIN SALES ON ALBUM.Code = SALES.Album
WHERE CopiesSold > 10000
HAVING COUNT(*) = /* Select difference from current year and came out year.*/
Can you help me with this? Thanks.
You can do this with an INNER JOIN, GROUP BY, and HAVING.
SELECT A.Code, A.Title
FROM ALBUM A
INNER JOIN SALES S ON S.Album = A.Code
GROUP BY A.Code, A.Title
HAVING MIN(S.CopiesSold) >= 10000
The HAVING clause will filter out albums whose minimum Copies Sold are < 10000.
EDIT
There was also a question about gaps in the Sales data, there are a number of ways to modify the above query to solve for this as well. One solution would be to use an embedded query to identify the correct number of years.
SELECT A.Code, A.Title
FROM ALBUM A
INNER JOIN SALES S ON S.Album = A.Code
GROUP BY A.Code, A.Title
HAVING MIN(S.CopiesSold) >= 10000 AND
COUNT(*) = (SELECT COUNT(DISTINCT Year) FROM SALES WHERE Year >= MIN(s.Year))
This solution assumes that at least one album by some artist was sold each year (a fairly safe bet). If you had a Years table there are simpler solutions. If the data is current there are also solutions that utilize DATEDIFF.
You can use correlated subqueries with EXISTS or NOT EXISTS respectively.
In one check if the maximum year minus the minimum year plus one is equal to the count of records with a defined year of an album. That way you make sure you don't get albums where there are figures missing for a year and you therefore cannot tell whether they sold 10000 or more or not. Also check that the maximum year is the current year not to miss gaps between the maximum year and the current year. (In the example code I will use the literal 2020 but there are means to get that dynamically. They depend on the DBMS however and you didn't state which one you're using.)
In the second one check that there's no record with undefined sales figures or sales figures lower than 10000 for the album. If no such record exists, all of the existing one have to have figures of 10000 or greater.
SELECT a1.code,
a1.title
FROM album a1
WHERE EXISTS (SELECT ''
FROM sales s1
WHERE s1.album = a1.code
HAVING max(s1.year) - min(s1.year) + 1 = count(s1.year)
AND max(s1.year) = 2020)
AND NOT EXISTS (SELECT *
FROM sales s2
WHERE s2.album = a1.code
AND s2.copiessold IS NULL
OR s2.copiessold < 10000);
I think the ALL keyword should work nicely here. Something like this:
SELECT * FROM Album
WHERE 10000 <= ALL (
SELECT CopiesSold FROM Sales
WHERE Sales.Album = Album.Code)
Related
this query shows a list of actors and how many times they acted in an action-type movie between 1980 and 2000. I'd like to get only the first rows but I didn't find an answer to my question.
Moreover, tell me if there is a better solution for my query.
FILM (CODFILM,TITLE,YEAR,GENRE)
ACTOR (CODACTOR,NAME,SURNAME)
CAST (CODFILM,CODACTOR)
YEAR type is Number and it's write-only the year release
SELECT CODACTOR, GENRE,count(CODACTOR)
FROM FILM NATURAL JOIN CAST T
WHERE GENRE = 'Action' AND YEAR BETWEEN 1980 AND 2000
GROUP BY CODACTOR,GENRE
HAVING COUNT(CODACTOR) >= ALL(
SELECT COUNT(CODACTOR)
FROM FILM NATURAL JOIN CAST
WHERE GENRE = 'Action' AND CODACTOR = T.CODACTOR AND ANNO BETWEEN 1980 AND 2000)
ORDER BY COUNT(CODACTOR) DESC;
Add this to your query
FETCH FIRST 1 ROWS ONLY
Docs
Example -
Top 3 compensated employees
This is available in version 12 and higher of the database.
Below that you could use pseudo column, ROWNUM
So I have two tables of sales, budget and actual.
"budget" has two columns: location and sales. For example,
location sales
24 $20000
36 $100300
40 $24700
Total $145000
"actual" has three columns: invoice_number, location, and sales. For example,
invoice location sales
10000 36 $5000
10001 40 $6000
10002 99 $7000
and so forth
Total $110000
In summary, "actual" records transactions at the invoice level, whereas "budget" is done at the location level only (no individual invoices).
I'm trying to create a summary table that lists actual and budget sales side by side, grouped by location. The total of the actual column should be $110000, and $145000 for budget. This is my attempt at it (on pgAdmin/ postgresql):
SELECT actual.location, SUM(actual.sales) AS actual_sales, SUM(budget.sales) AS budget_sales
FROM actual LEFT JOIN budget
ON actual.location = budget.location
GROUP BY actual.location;
I used LEFT JOIN because "actual" has locations that "budget" doesn't have (e.g. location 99).
I ended up with some gigantic numbers ($millions) on both the actual_sales and budget_sales columns, far exceeding the total actual ($110000) or budget sales ($145,000).
Is this because the way I wrote my query is basically asking SQL to join each invoice in "actual" to each line in "budget," therefore duplicating things many times over? If so how should I have written this?
Thanks in advance!
Based on your description, you seem to have duplicates in both tables. There are various ways to solve this problem. Here is one using union all and group by:
select Location,
sum(actual_sales) as actual_sales,
sum(budget_sales) as budget_sales
from ((select a.location, a.sales as actual_sales, null as budget_sales
from actual a
) union all
(select b.location, null, b.sales
from budget b
)
) ab
group by location;
This structure guarantees that each value is counted only once, regardless of the table.
The query looks fine to me. However, it is difficult to find out why the figures are wrong. My suggestion is that you do the sum by location separately for budget and actual into 2 temporary tables, and later put them together using LEFT JOIN.
Yes, you're joining the budget in once for each actual sales row. However, your Actual Sales sum shouldn't have been larger unless there were multiple budget rows for the same location. You should check for that, because it doesn't sound like there should be.
What you need to do in a case like this is sum the actual sales first in a CTE or subquery, then later join the result to the budget. That way you only have one row for each location. This does it for the actual sales. If you really do have more than one row for a location for budget as well, you might need to subquery the budget as well the same way.
Select Act.Location, Act.actual_sales, budget.sales as budget_sales
From
(
SELECT actual.location, SUM(actual.sales) AS actual_sales
FROM actual
GROUP BY actual.location
) Act
left join budget on Act.location = budget.location
Gordon's suggestion is good, an alternative using WITH statements is:
WITH aloc AS (
SELECT location, SUM(sales) FROM actual GROUP BY 1
), bloc AS (
SELECT location, SUM(sales) FROM budget GROUP BY 1
)
SELECT location, a.sum AS actual_sales, b.sum AS budget_sales
FROM aloc a LEFT JOIN bloc b USING (location)
This is equivalent to:
SELECT location, a.sum AS actual_sales, b.sum AS budget_sales
FROM (SELECT location, SUM(sales) FROM actual GROUP BY 1) a LEFT JOIN
(SELECT location, SUM(sales) FROM budget GROUP BY 1) b USING (location)
but I find WITH statements more readable.
The purpose of the subqueries is to get tables into a state where a row means something relevant, i.e. aloc contains a row per location, and hence cause the join to evaluate to what you want.
I've got a database that holds information about volunteers and their participation in a range of events.
The following query gives me a list of their names and total attendances
SELECT
volunteers.last_name,
volunteers.first_name,
count (bookings.id)
FROM
volunteers,
bookings
WHERE
volunteers.id = bookings.volunteer_id
GROUP BY
volunteers.last_name,
volunteers.first_name
I want the result table to show the distinct number of attendances and how many there are of each; So if five people did one event it'd display 1 in the first column and 5 in the second and so on.
Thanks
If I understand correctly, you want what I call a "histogram of histograms" query:
select numvolunteers, count(*) as numevents, min(eventid), max(eventid)
from (select b.eventid, count(*) as numvolunteers
from bookings b
group by b.eventid
) b
group by numvolunteers
order by numvolunteers;
The first column is the number of volunteers booked for an "event". The second is the number of events where this occurs. The last two columns are just examples of events that have the given number of volunteers.
I have seen some close answers and I have been trying to adapt them to Access 2013, but I can't seem to get it to work. I have two queries:
First query returns
original_staff_data
Month
Year
staff_uid
staff_abbrev
employee_name
staff_salary
It pulls this from tables staff, and salary_by_month and employee_name and number_of_days_at_spec_building (this records where they check in when they work)
transaction_data_by_staff.total
Month
Year
staff_uid
total_revenue
totat_profit
this also pulls information from staff, but sums up over multiple dates in a transaction table creating a cumulative value for each staff_uid so I can't combine the two queries directly.
My problem is I want to create a query that brings results from both. However, not all staff members in Q1 will be in Q2 every day/week/month (vacations, etc) and since I want to ultimately create a final results:
Final_Result
Month
Year
staff_uid
staff_abbrev
employee_name
staff_salary
total_revenue
total_profit
The SQL:
SELECT
original_staff_data.*
, transaction_data_by_staff.total_rev
, transaction_data_by_staff.total_profit
FROM transaction_data_by_staff
RIGHT JOIN original_staff_data
ON (
transaction_data_by_staff.year = original_staff_data.year
AND transaction_data_by_staff.month = original_staff_data.month
) WHERE transaction_data_by_staff.[staff_uid] = [original_staff_data].[staff_uid];
I would like it if there is no revenue or profit that month from that employee, it makes those values 0. I have tried join (specifically RIGHT join with Q1 as the RIGHT join) and it doesn't seem to work, I still only get the subset. There are originally in the original_staff_data query 750 entries so therefore there should be in the final query 750 entries, I am only getting 252, which is the total in transaction_data_by_staff. Any clue on how the ACCESS 2013 SQL should look?
Thanks
Jon
Move the link by stuff_uid to the ON clause, like this:
SELECT original_staff_data.*, transaction_data_by_staff.total_rev, transaction_data_by_staff.total_profit
FROM transaction_data_by_staff RIGHT JOIN original_staff_data ON (transaction_data_by_staff.year = original_staff_data.year) AND (transaction_data_by_staff.month = original_staff_data.month)
AND (((transaction_data_by_staff.[staff_uid])=[original_staff_data].[staff_uid]));
Edited
I am running into an error and I know what is happening but I can't see what is causing it. Below is the sql code I am using. Basically I am getting the general results I want, however I am not accurately giving the query the correct 'where' clause.
If this is of any assistance. The count is coming out as this:
Total Tier
1 High
2 Low
There are 4 records in the Enrollment table. 3 are active, and 1 is not. Only 2 of the records should be displayed. 1 for High, and 1 for low. The second Low record that is in the total was flagged as 'inactive' on 12/30/2010 and reflagged again on 1/12/2011 so it should not be in the results. I changed the initial '<=' to '=' and the results stayed the same.
I need to exclude any record from Enrollments_Status_Change that where the "active_status" was changed to 0 before the date.
SELECT COUNT(dbo.Enrollments.Customer_ID) AS Total,
dbo.Phone_Tier.Tier
FROM dbo.Phone_Tier as p
JOIN dbo.Enrollments as eON p.Phone_Model = e.Phone_Model
WHERE (e.Customer_ID NOT IN
(Select Customer_ID
From dbo.Enrollment_Status_Change as Status
Where (Change_Date >'12/31/2010')))
GROUP BY dbo.Phone_Tier.Tier
Thanks for any assistance and I apologize for any confusion. This is my first time here and i'm trying to correct my etiquette on the fly.
If you don't want any of the fields from that table dbo.Enrollment_Status_Change, and you don't seem to use it in any way — why even include it in the JOINs? Just leave it out.
Plus: start using table aliases. This is very hard to read if you use the full table name in each JOIN condition and WHERE clause.
Your code should be:
SELECT
COUNT(e.Customer_ID) AS Total, p.Tier
FROM
dbo.Phone_Tier p
INNER JOIN
dbo.Enrollments e ON p.Phone_Model = e.Phone_Model
WHERE
e.Active_Status = 1
AND EXISTS (SELECT DISTINCT Customer_ID
FROM dbo.Enrollment_Status_Change AS Status
WHERE (Change_Date <= '12/31/2010'))
GROUP BY
p.Tier
Also: most likely, your EXISTS check is wrong — since you didn't post your table structures, I can only guess — but my guess would be:
AND EXISTS (SELECT * FROM dbo.Enrollment_Status_Change
WHERE Change_Date <= '12/31/2010' AND CustomerID = e.CustomerID)
Check for existence of any entries in dbo.Enrollment_Status_Change for the customer defined by e.CustomerID, with a Change_Date before that cut-off date. Right?
Assuming you want to:
exclude all customers whose latest enrollment_status_change record was since the start of 2011
but
include all customers whose latest enrollment_status_change record was earlier than the end of 2010 (why else would you have put that EXISTS clause in?)
Then this should do it:
SELECT COUNT(e.Customer_ID) AS Total,
p.Tier
FROM dbo.Phone_Tier p
JOIN dbo.Enrollments e ON p.Phone_Model = e.Phone_Model
WHERE dbo.Enrollments.Active_Status = 1
AND e.Customer_ID NOT IN (
SELECT Customer_ID
FROM dbo.Enrollment_Status_Change status
WHERE (Change_Date >= '2011-01-01')
)
GROUP BY p.Tier
Basically, the problem with your code is that joining a one-to-many table will always increase the row count. If you wanted to exclude all the records that had a matching row in the other table this would be fine -- you could just use a LEFT JOIN and then set a WHERE clause like Customer_ID IS NULL.
But because you want to exclude a subset of the enrollment_status_change table, you must use a subquery.
Your intention is not clear from the example given, but if you wanted to exclude anyone who's enrollment_status_change as before 2011, but include those who's status change was since 2011, you'd just swap the date comparator for <.
Is this any help?