I have 3 tables of purchases in the following format:
date | company_id | apple_txn_amt
date | company_id | orange_txn_amt
date | company_id | pear_txn_amt
There are multiple purchases/sales daily for many companies. I'm trying to join and group so there is only 1 date per company along with total fruit balance:
date | company_id | total_apple_balance | total_apple_orange_balance | total_pear_balance
I have built a query for a similar case earlier, and used 2 joins. But this was for only one company's data so I was only joining on date=date for each table. Process for each table was: gather buys, sells, union those two, union to a new table with generate_series() to insert 0s for days missing, calculate daily delta, and group by day to have a running total. Then something like:
SELECT
apple.day
apple.total
orange.total
pear.total
(apple + orange + pear) AS total_fruit
FROM apple
JOIN orange ON orange.date = apple.date
JOIN pear ON pear.date = apple.date
ORDER BY day
It's like I need to JOIN ON date and company id but from what I can tell this isn't possible.
Should I approach this in a different way?
Sure you can add the company_id like
SELECT
apple.day
apple.total
orange.total
pear.total
(apple.total + orange.total + pear.total) AS total_fruit
FROM apple
JOIN orange ON orange.date = apple.date AND orange.company_id = apple.company_id
JOIN pear ON pear.date = apple.date AND pear.company_id = apple.company_id
ORDER BY day
But the design of your database isn't right, if circumstances don't require it.
you would not have 3 tables, you would have only one with Fruit type as another column, to differentiate them
Related
I need to merge two tables, spring_stats and summer_stats, into one table in which some of the columns are the same and thus should be summed.
Each table contains (among others) the fields hunter_id, year, fowl, deer, bears where the last three represent numeric amount each hunter has caught.
The end result should be
hunter_id, year, spring.fowl + summer.fowl, spring.deer + summer.deer, etc
HOWEVER, some of the hunters may not have participated in the summer session but participated in the spring session (or vice versa). In this case the standard
SELECT hunter_id, year, spring.fowl + summer.fowl AS total_fowl, ... FROM spring, summer
WHERE spring.hunter_id = summer.hunter_id AND spring.year = summer.year
would not work as hunters who were active in only the spring or summer session would not be recorded and included, whereas I need all hunters included, regardless of whether they were active in only one session or both.
You are using an ancient type of table join. Instead adopt the newer (since the early 90s) join syntax. Here you want a FULL OUTER JOIN:
SELECT COALESCE(summer.hunter_id, spring.hunter_id) as hunter_id,
COALESCE(summer.year, spring.year) as year,
spring.fowl + summer.fowl AS total_fowl, ...
FROM spring
FULL OUTER JOIN summer
ON spring.hunter_id = summer.hunter_id
AND spring.year = summer.year
You can read up about FULL OUTER JOIN here at the postgres documentation site:
First, an inner join is performed. Then, for each row in T1 that does
not satisfy the join condition with any row in T2, a joined row is
added with null values in columns of T2. Also, for each row of T2 that
does not satisfy the join condition with any row in T1, a joined row
with null values in the columns of T1 is added.
The COALESCE() function will first use the hunter_id from the summer table unless it's NULL (due to the FULL OUTER JOIN) in which case it will pick the hunter_id from the spring table.
I think it's also worth mentioning that having tables specific to your seasons may not make sense. Instead a single table where Season is just an added column may be a better schema:
season | year | hunter_id | animal | animal_count
summer | 2020 | 1 | fowl | 3
spring | 2020 | 1 | deer | 2
summer | 2020 | 2 | fowl | 4
spring | 2021 | 3 | fowl | 1
Now your query is:
SELECT
hunter_id,
year,
sum(CASE WHEN animal='fowl' THEN animal_count END) as fowl_total,
sum(CASE WHEN animal='dear' THEN animal_count END) as deer_total
FROM this_new_table
GROUP BY hunter_id, year
I take a Database course in which we have listings of AirBnBs and need to be able to do some SQL queries in the Relationship-Model we made from the data, but I struggle with one in particular :
I have two tables that we are interested in, Billing and Amenities. The first one have the id and price of listings, the second have id and wifi (let's say, to simplify, that it equals 1 if there is Wifi, 0 otherwise). Both have other attributes that we don't really care about here.
So the query is, "What is the difference in the average price of listings with and without Wifi ?"
My idea was to build to JOIN-tables, one with listings that have wifi, the other without, and compare them easily :
SELECT avg(B.price - A.price) as averagePrice
FROM (
SELECT Billing.price, Billing.id
FROM Billing
INNER JOIN Amenities
ON Billing.id = Amenities.id
WHERE Amenities.wifi = 0
) A, (
SELECT Billing.price, Billing.id
FROM Billing
INNER JOIN Amenities
ON Billing.id = Amenities.id
WHERE Amenities.wifi = 1) B
WHERE A.id = B.id;
Obviously this doesn't work... I am pretty sure that there is a far easier solution to it tho, what do I miss ?
(And by the way, is there a way to compute the absolute between the difference of price ?)
I hope that I was clear enough, thank you for your time !
Edit : As mentionned in the comments, forgot to say that, but both tables have idas their primary key, so that there is one row per listing.
Just use conditional aggregation:
SELECT AVG(CASE WHEN a.wifi = 0 THEN b.price END) as avg_no_wifi,
AVG(CASE WHEN a.wifi = 1 THEN b.price END) as avg_wifi
FROM Billing b JOIN
Amenities a
ON b.id = a.id
WHERE a.wifi IN (0, 1);
You can use a - if you want the difference instead of the specific values.
Let's assume we're working with data like the following (problems with your data model are noted below):
Billing
+------------+---------+
| listing_id | price |
+------------+---------+
| 1 | 1500.00 |
| 2 | 1700.00 |
| 3 | 1800.00 |
| 4 | 1900.00 |
+------------+---------+
Amenities
+------------+------+
| listing_id | wifi |
+------------+------+
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
+------------+------+
Notice that I changed "id" to "listing_id" to make it clear what it was (using "id" as an attribute name is problematic anyways). Also, note that one listing doesn't have an entry in the Amenities table. Depending on your data, that may or may not be a concern (again, refer to the bottom for a discussion of your data model).
Based on this data, your averages should be as follows:
Listings with wifi average $1600 (Listings 1 and 2)
Listings without wifi (just 3) average 1800).
So the difference would be $200.
To achieve this result in SQL, it may be helpful to first get the average cost per amenity (whether wifi is offered). This would be obtained with the following query:
SELECT
Amenities.wifi AS has_wifi,
AVG(Billing.price) AS avg_cost
FROM Billing
INNER JOIN Amenities ON
Amenities.listing_id = Billing.listing_id
GROUP BY Amenities.wifi
which gives you the following results:
+----------+-----------------------+
| has_wifi | avg_cost |
+----------+-----------------------+
| 0 | 1800.0000000000000000 |
| 1 | 1600.0000000000000000 |
+----------+-----------------------+
So far so good. So now we need to calculate the difference between these 2 rows. There are a number of different ways to do this, but one is to use a CASE expression to make one of the values negative, and then simply take the SUM of the result (note that I'm using a CTE, but you can also use a sub-query):
WITH
avg_by_wifi(has_wifi, avg_cost) AS
(
SELECT Amenities.wifi, AVG(Billing.price)
FROM Billing
INNER JOIN Amenities ON
Amenities.listing_id = Billing.listing_id
GROUP BY Amenities.wifi
)
SELECT
ABS(SUM
(
CASE
WHEN has_wifi = 1 THEN avg_cost
ELSE -1 * avg_cost
END
))
FROM avg_by_wifi
which gives us the expected value of 200.
Now regarding your data model:
If both your Billing and Amenities table only have 1 row for each listing, it makes sense to combine them into 1 table. For example: Listings(listing_id, price, wifi)
However, this is still problematic, because you probably have a bunch of other amenities you want to model (pool, sauna, etc.) So you might want to model a many-to-many relationship between listings and amenities using an intermediate table:
Listings(listing_id, price)
Amenities(amenity_id, amenity_name)
ListingsAmenities(listing_id, amenity_id)
This way, you could list multiple amenities for a given listing without having to add additional columns. It also becomes easy to store additional information about an amenity: What's the wifi password? How deep is the pool? etc.
Of course, using this model makes your original query (difference in average cost of listings by wifi) a bit tricker, but definitely still doable.
Greetings Benevolent Gods of Stackoverflow,
I am presently struggling to get a spatially enabled query to work for a SQL assignment I am working on. The wording is as follows:
SELECT PURCHASES.TotalPrice, STORES.GeoLocation, STORES.StoreName
FROM MuffinShop
join (SELECT SUM(PURCHASES.TotalPrice) AS StoreProfit, STORES.StoreName
FROM PURCHASES INNER JOIN STORES ON PURCHASES.StoreID = STORES.StoreID
GROUP BY STORES.StoreName
HAVING (SUM(PURCHASES.TotalPrice) > 600))
What I am trying to do with this query is perform a function query (like avg, sum etc) and get the spatial information back as well. Another example of this would be:
SELECT STORES.StoreName, AVG(REVIEWS.Rating),Stores.Shape
FROM REVIEWS CROSS JOIN
STORES
GROUP BY STORES.StoreName;
This returns a Column 'STORES.Shape' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause. error message.
I know I require a sub query to perform this task, I am just having endless trouble getting it to work. Any help at all would be wildly appreciated.
There are two parts to this question, I would tackle the first problem with the following logic:
List all the store names and their respective geolocations
Get the profit for each store
With that in mind, you need to use the STORES table as your base, then bolt the profit onto it through a sub query or an apply:
SELECT s.StoreName
,s.GeoLocation
,p.StoreProfit
FROM STORES s
INNER JOIN (
SELECT pu.StoreId
,StoreProfit = SUM(pu.TotalPrice)
FROM PURCHASES pu
GROUP BY pu.StoreID
) p
ON p.StoreID = s.StoreID;
This one is a little more efficient:
SELECT s.StoreName
,s.GeoLocation
,profit.StoreProfit
FROM STORES s
CROSS APPLY (
SELECT StoreProfit = SUM(p.TotalPrice)
FROM PURCHASES p
WHERE p.StoreID = s.StoreID
GROUP BY p.StoreID
) profit;
Now for the second part, the error that you are receiving tells you that you need to GROUP BY all columns in your select statement with the exception of your aggregate function(s).
In your second example, you are asking SQL to take an average rating for each store based on an ID, but you are also trying to return another column without including that inside the grouping. I will try to show you what you are asking SQL to do and where the issue lies with the following examples:
-- Data
Id | Rating | Shape
1 | 1 | Triangle
1 | 4 | Triangle
1 | 1 | Square
2 | 1 | Triangle
2 | 5 | Triangle
2 | 3 | Square
SQL Server, please give me the average rating for each store:
SELECT Id, AVG(Rating)
FROM Store
GROUP BY StoreId;
-- Result
Id | Avg(Rating)
1 | 2
2 | 3
SQL Server, please give me the average rating for each store and show its shape in the result (but don't group by it):
SELECT Id, AVG(Rating), Shape
FROM Store
GROUP BY StoreId;
-- Result
Id | Avg(Rating) | Shape
1 | 2 | Do I show Triangle or Square ...... ERROR!!!!
2 | 3 |
It needs to be told to get the average for each store and shape:
SELECT Id, AVG(Rating), Shape
FROM Store
GROUP BY StoreId, Shape;
-- Result
Id | Avg(Rating) | Shape
1 | 2.5 | Triangle
1 | 1 | Square
2 | 3 | Triangle
2 | 3 | Square
As in any spatial query you need an idea of what your final geometry will be. It looks like you are attempting to group by individual stores but delivering an average rating from the subquery. So if I'm reading it right you are just looking to get the stores shape info associated with the average ratings?
Query the stores table for the shape field and join the query you use to get the average rating
select a.shape
b.*
from stores a inner join (your Average rating query with group by here) b
on a.StoreID = b.Storeid
Hi stackoverflow users
I'm having a bit of a problem trying to combine SUM, MAX and WHERE in one query and after an intense Google search (my search engine skills usually don't fail me) you are my last hope to understand and fix the following issue.
My goal is to count people in a certain period of time and because a person can visit more than once in said period, I'm using MAX. Due to the fact that I'm defining people as male (m) or female (f) using a string (for statistic purposes), CHAR_LENGTH returns the numbers I'm in need of.
SELECT SUM(max_pers) AS "People"
FROM (
SELECT "guests"."id", MAX(CHAR_LENGTH("guests"."gender")) AS "max_pers"
FROM "guests"
GROUP BY "guests"."id")
So far, so good. But now, as stated before, I'd like to only count the guests which visited in a certain time interval (for statistic purposes as well).
SELECT "statistic"."id", SUM(max_pers) AS "People"
FROM (
SELECT "guests"."id", MAX(CHAR_LENGTH("guests"."gender")) AS "max_pers"
FROM "guests"
GROUP BY "guests"."id"),
"statistic", "guests"
WHERE ( "guests"."arrival" <= "statistic"."from" AND "guests"."departure" >= "statistic"."to")
GROUP BY "statistic"."id"
This query returns the following, x = desired result:
x * (x+1)
So if the result should be 3, it's 12. If it should be 5, it's 30 etc.
I probably could solve this algebraic but I'd rather understand what I'm doing wrong and learn from it.
Thanks in advance and I'm certainly going to answer all further questions.
PS: I'm using LibreOffice Base.
EDIT: An example
guests table:
ID | arrival | departure | gender |
10 | 1.1.14 | 10.1.14 | mf |
10 | 15.1.14 | 17.1.14 | m |
11 | 5.1.14 | 6.1.14 | m |
12 | 10.2.14 | 24.2.14 | f |
13 | 27.2.14 | 28.2.14 | mmmmmf |
statistic table:
ID | from | to | name |
1 | 1.1.14 | 31.1.14 |January | expected result: 3
2 | 1.2.14 | 28.2.14 |February| expected result: 7
MAX(...) is the wrong function: You want COUNT(DISTINCT ...).
Add proper join syntax, simplify (and remove unnecessary quotes) and this should work:
SELECT s.id, COUNT(DISTINCT g.id) AS People
FROM statistic s
LEFT JOIN guests g ON g.arrival <= s."from" AND g.departure >= s."too"
GROUP BY s.id
Note: Using LEFT join means you'll get a result of zero for statistics ids that have no guests. If you would rather no row at all, remove the LEFT keyword.
You have a very strange data structure. In any case, I think you want:
SELECT s.id, sum(numpersons) AS People
FROM (select g.id, max(char_length(g.gender)) as numpersons
from guests g join
statistic s
on g.arrival <= s."from" AND g.departure >= s."too"
group by g.id
) g join
GROUP BY s.id;
Thanks for all your inputs. I wasn't familiar with JOIN but it was necessary to solve my problem.
Since my databank is designed in german, I made quite the big mistake while translating it and I'm sorry if this caused confusion.
Selecting guests.id and later on grouping by guests.id wouldn't make any sense since the id is unique. What I actually wanted to do is select and group the guests.adr_id which links a visiting guest to an adress databank.
The correct solution to my problem is the following code:
SELECT statname, SUM (numpers) FROM (
SELECT statistic.name AS statname, guests.adr_id, MAX( CHAR_LENGTH( guests.gender ) ) AS numpers
FROM guests
JOIN statistics ON (guests.arrival <= statistics.too AND guests.departure >= statistics.from )
GROUP BY guests.adr_id, statistic.name )
GROUP BY statname
I also noted that my database structure is a mess but I created it learning by doing and haven't found any time to rewrite it yet. Next time posting, I'll try better.
I have the following "COMPANIES_BY_NEWS_REPUTATION" in my JavaDB database (this is some random data just to represent the structure)
COMPANY | NEWS_HASH | REPUTATION | DATE
-------------------------------------------------------------------
Company A | 14676757 | 0.12345 | 2011-05-19 15:43:28.0
Company B | 454564556 | 0.78956 | 2011-05-24 18:44:28.0
Company C | 454564556 | 0.78956 | 2011-05-24 18:44:28.0
Company A | -7874564 | 0.12345 | 2011-05-19 15:43:28.0
One news_hash may relate to several companies while a company can relate to several news_hashes as well. Reputation and date are bound to the news_hash.
What I need to do is calculate the average reputation of last 5 news for every company. In order to do that I somehow feel that I need to user 'order by' and 'offset' in a subquery as shown in the code below.
select COMPANY, avg(REPUTATION) from
(select * from COMPANY_BY_NEWS_REPUTATION order by "DATE" desc
offset 0 rows fetch next 5 row only) as TR group by COMPANY;
However, JavaDB allows neither ORDER BY, nor OFFSET in a subquery. Could anyone suggest a working solution for my problem please?
Which version of JavaDB are you using? According to the chapter TableSubquery in the JavaDB documentation, table subqueries do support order by and fetch next, at least in version 10.6.2.1.
Given that subqueries can be ordered and the size of the result set can be limited, the following (untested) query might do what you want:
select COMPANY, (select avg(REPUTATION)
from (select REPUTATION
from COMPANY_BY_NEWS_REPUTATION
where COMPANY = TR.COMPANY
order by DATE desc
fetch first 5 rows only))
from (select distinct COMPANY
from COMPANY_BY_NEWS_REPUTATION) as TR
This query retrieves all distinct company names from COMPANY_BY_NEWS_REPUTATION, then retrieves the average of the last five reputation rows for each company. I have no idea whether it will perform sufficiently, that will likely depend on the size of your data set and what indexes you have in place.
If you have a list of unique company names in another table, you can use that instead of the select distinct ... subquery to retrieve the companies for which to calculate averages.