I have the following tables:
Students(id, name, surname)
Courses(course id)
Course_Signup(id, student_id, course_id, year)
Grades(signup_id, mark)
I want to display all the students(id, name, surname) with their final grade (where final grade = avg of the grades of all courses), but only for the students that have passed all the courses for which they have sign-up in the current year.
This is what I tried:
SELECT s."id", s."name", s."surname", AVG(g."mark") AS "finalGrade"
FROM "STUDENT" s,
"course sign-up" csn
join "GRADES" g
on csn."id" = g."signup_id"
WHERE csn."year" >= '01-01-2022'
HAVING "finalGrade" >= 5.00
GROUP BY s."id"
However, after adding the last 2 lines, regarding the finalGrade condition, I get an invalid identifier error. Why is that?
Uh, oh. Did you really create tables using lower letter case names enclosed into double quotes? If so, get rid of them (the sooner, the better) because they only cause problems.
Apart from that, uniformly use joins - in your from clause there's the student table which isn't joined to any other table and results in cross join.
Don't compare dates to strings; use date literal (as I did), or to_date function with appropriate format model.
As of error you got: you can't reference expression's alias ("finalGrade") as is in the having clause - use the whole expression.
Also, group by should contain all non-aggregated columns from the select column list.
This "fixes" error you got, but - I suggest you consider everything I said:
SELECT s."id", s."name", s."surname", AVG(g."mark") AS "finalGrade"
FROM "STUDENT" s,
"course sign-up" csn
join "GRADES" g
on csn."id" = g."signup_id"
WHERE csn."year" >= date '2022-01-01'
GROUP BY s."id", s."name", s."surname"
HAVING AVG(g."mark") >= 5.00
Given the following db structure:
Regions
id
name
1
EU
2
US
3
SEA
Customers:
id
name
region
1
peter
1
2
henry
1
3
john
2
There is also a PL/pgSQL function in place, defined as sendShipment() which takes (among other things) a sender and a receiver customer ID.
There is a business constraint around this which requires us to verify that both sender and receiver sit in the same region - and we need to do this as part of sendShipment(). So from within this function, we need to query the customer table for both the sender and receiver ID and verify that both their region ID is identical. We will also need to ID itself for further processing down the line.
So maybe something like this:
SELECT DISTINCT region FROM customers WHERE id IN (?, ?)
The problem with this is that the result will be either an array (if the customers are not within the same region) or a single value.
Is there are more elegant way of solving this constraint? I was thinking of SELECT INTO and use a temporary table, or I could SELECT COUNT(DISTINCT region) and then do another SELECT for the actual value if the count is less than 2, but I'd like to avoid the performance hit if possible.
There is also a PL/pgSQL function in place, defined as sendShipment() which takes (among other things) a sender and a receiver customer ID.
There is a business constraint around this which requires us to verify that both sender and receiver sit in the same region - and we need to do this as part of sendShipment(). So from within this function, we need to query the customer table for both the sender and receiver ID and verify that both their region ID is identical. We will also need to ID itself for further processing down the line.
This query should work:
WITH q AS (
SELECT
COUNT( * ) AS CountCustomers,
COUNT( DISTINCT c.Region ) AS CountDistinctRegions,
-- MIN( c.Region ) AS MinRegion
FIRST_VALUE( c.Region ) OVER ( ORDER BY c.Region ) AS MinRegion
FROM
Customers AS c
WHERE
c.CustomerId = $senderCustomerId
OR
c.CustomerId = $receiverCustomerId
)
SELECT
CASE WHEN q.CountCustomers = 2 AND q.CountDistinctRegions = 2 THEN 'OK' ELSE 'BAD' END AS "Status",
CASE WHEN q.CountDistinctRegions = 2 THEN q.MinRegion END AS SingleRegion
FROM
q
The above query will always return a single row with 2 columns: Status and SingleRegion.
SQL doesn't have a "SINGLE( col )" aggregate function (i.e. a function that is NULL unless the aggregation group has a single row), but we can abuse MIN (or MAX) with a CASE WHEN COUNT() in a CTE or derived-table as an equivalent operation.
Alternatively, windowing-functions could be used, but annoyingly they don't work in GROUP BY queries despite being so similar, argh.
Once again, this is the ISO SQL committee's fault, not PostgreSQL's.
As your Region column is UUID you cannot use it with MIN, but I understand it should work with FIRST_VALUE( c.Region ) OVER ( ORDER BY c.Region ) AS MinRegion.
As for the columns:
The Status column is either 'OK' or 'BAD' based on those business-constraints you mentioned. You might want to change it to a bit column instead of a textual one, though.
The SingleRegion column will be NOT NULL (with a valid region) if CountDistinctRegions = 2 regardless of CountCustomers, but feel free to change that, just-in-case you still want that info.
For anybody else who's interested in a simple solution, I finally came up with the (kind of obvious) way to do it:
SELECT
r.region
FROM
customers s
INNER JOIN customers r ON
s.region = r.region
WHERE s.id = 'sender_id' and r.id = 'receiver_id';
Huge credit to SELECT DISTINCT to return at most one row who helped me out a lot on this and also posted a viable solution.
I have project on CRM which maintains product sales order for every organization.
I want to count everyday sold stock which I have managed to do by looping over by date but obviously it is a ridiculous method and taking more time and memory.
Please help me to find out it in single query. Is it possible?
Here is my database structure for your reference.
product : id (PK), name
organization : id (PK), name
sales_order : id (PK), product_id (FK), organization_id (FK), sold_stock, sold_date(epoch time)
Expected Output for selected month :
organization | product | day1_sold_stock | day2_sold_stock | ..... | day30_sold_stock
http://sqlfiddle.com/#!15/e1dc3/3
Create tablfunc :
CREATE EXTENSION IF NOT EXISTS tablefunc;
Query :
select "proId" as ProductId ,product_name as ProductName,organizationName as OrganizationName,
coalesce( "1-day",0) as "1-day" ,coalesce( "2-day",0) as "2-day" ,coalesce( "3-day",0) as "3-day" ,
coalesce( "4-day",0) as "4-day" ,coalesce( "5-day",0) as "5-day" ,coalesce( "6-day",0) as "6-day" ,
coalesce( "7-day",0) as "7-day" ,coalesce( "8-day",0) as "8-day" ,coalesce( "9-day",0) as "9-day" ,
coalesce("10-day",0) as "10-day" ,coalesce("11-day",0) as "11-day" ,coalesce("12-day",0) as "12-day" ,
coalesce("13-day",0) as "13-day" ,coalesce("14-day",0) as "14-day" ,coalesce("15-day",0) as"15-day" ,
coalesce("16-day",0) as "16-day" ,coalesce("17-day",0) as "17-day" ,coalesce("18-day",0) as "18-day" ,
coalesce("19-day",0) as "19-day" ,coalesce("20-day",0) as "20-day" ,coalesce("21-day",0) as"21-day" ,
coalesce("22-day",0) as "22-day" ,coalesce("23-day",0) as "23-day" ,coalesce("24-day",0) as "24-day" ,
coalesce("25-day",0) as "25-day" ,coalesce("26-day",0) as "26-day" ,coalesce("27-day",0) as"27-day" ,
coalesce("28-day",0) as "28-day" ,coalesce("29-day",0) as "29-day" ,coalesce("30-day",0) as "30-day" ,
coalesce("31-day",0) as"31-day"
from crosstab(
'select hist.product_id,pr.name,o.name,EXTRACT(day FROM TO_TIMESTAMP(hist.sold_date/1000)),sum(sold_stock)
from sales_order hist
left join product pr on pr.id = hist.product_id
left join organization o on o.id = hist.organization_id
where EXTRACT(MONTH FROM TO_TIMESTAMP(hist.sold_date/1000)) =5
and EXTRACT(YEAR FROM TO_TIMESTAMP(hist.sold_date/1000)) = 2017
group by hist.product_id,pr.name,EXTRACT(day FROM TO_TIMESTAMP(hist.sold_date/1000)),o.name
order by o.name,pr.name',
'select d from generate_series(1,31) d')
as ("proId" int ,product_name text,organizationName text,
"1-day" float,"2-day" float,"3-day" float,"4-day" float,"5-day" float,"6-day" float
,"7-day" float,"8-day" float,"9-day" float,"10-day" float,"11-day" float,"12-day" float,"13-day" float,"14-day" float,"15-day" float,"16-day" float,"17-day" float
,"18-day" float,"19-day" float,"20-day" float,"21-day" float,"22-day" float,"23-day" float,"24-day" float,"25-day" float,"26-day" float,"27-day" float,"28-day" float,
"29-day" float,"30-day" float,"31-day" float);
Please note, use PostgreSQL Crosstab Query. I have used coalesce for handling null values(Crosstab Query to show "0" when there is null data to return).
Following query will help to find the same:
select o.name,
p.name,
sum(case when extract (day from to_timestamp(sold_date))=1 then sold_stock else 0 end)day1_sold_stock,
sum(case when extract (day from to_timestamp(sold_date))=2 then sold_stock else 0 end)day2_sold_stock,
sum(case when extract (day from to_timestamp(sold_date))=3 then sold_stock else 0 end)day3_sold_stock,
from sales_order so,
organization o,
product p
where so.organization_id=o.id
and so.product_id=p.id
group by o.name,
p.name;
I just provided logic to find for 3 days, you can implement the same for rest of the days.
basically first do basic joins on id, and then check if each date(after converting epoch to timestamp and then extract day).
You have a few options here but it is important to understand the limitations first.
The big limitation is that the planner needs to know the record size before the planning stage, so this has to be explicitly defined, not dynamically defined. There are various ways of getting around this. At the end of the day, you are probably going to have somethign like Bavesh's answer, but there are some tools that may help.
Secondly, you may want to aggregate by date in a simple query joining the three tables and then pivot.
For the second approach, you could:
You could do a simple query and then pull the data into Excel or similar and create a pivot table there. This is probably the easiest solution.
You could use the tablefunc extension to create the crosstab for you.
Then we get to the first problem which is that if you are always doing 30 days, then it is easy if tedious. But if you want to do every day for a month, you run into the row length problem. Here what you can do is create a dynamic query in a function (pl/pgsql) and return a refcursor. In this case the actual planning takes place in the function and the planner doesn't need to worry about it on the outer level. Then you call FETCH on the output.
I have an SQL sentence :
SELECT application.id,title,url,company.name AS company_name,package_name,ranking,date,platform,country.name AS country_name,collection.name AS collection_name,category.name AS category_name FROM application
JOIN application_history ON application_history.application_id = application.id
JOIN company ON application.company_id = company.id
JOIN country ON application_history.country_id = country.id
JOIN collection ON application_history.collection_id = collection.id
JOIN category ON application_history.category_id = category.id
WHERE application.platform=0
AND country.name ='CZ'
AND collection.name='topfreeapplications'
AND category.name='UTILITIES'
AND application_history.ranking <= 10
AND date::date BETWEEN date (CURRENT_DATE - INTERVAL '1 month') AND CURRENT_DATE
ORDER BY application_history.ranking ASC
It produces this result :
I'd like to add both a column average ranking for a given package, and a column number of appearances, which would count the number a package appears in the list. I'd also like to Group results by package_name, so that I don't have redundancies.
So far, I've tried to add a GROUP BY By clause before the ORDER BY :
GROUP BY package_name
But it returns me an error :
column "application.id" must appear in the GROUP BY clause or be used in an aggregate function
If I add each and every column it asks me for, it doesn't work.
I have also tried to count the number of package names, by adding after the SELECT :
COUNT(package_name) AS count
It produces a similar error.
How could I get the result I'm looking for ? Should I make two queries instead, or is it possible to get everything at once ?
I precise I have looked at other answers on S.O, but none of them tries to make the COUNT on a "produced" column.
Thank you for your help.
Edit :
Here is the result I expected at first :
Although Gordon's advice didn't give me the proper result it put me on the good track, when I read this :
From the docs : "Unlike regular aggregate functions, use of a window function does not cause rows to become grouped into a single output row."
So I came back to using COUNT and AVG alone. My problem was that I wanted to display the ranking column and date to check whether things were right. But putting these column into the Select prevented the GROUP BY to work as expected, as mentioned by Jarlh in the comments.
The working query :
SELECT application.id,title,url,company.name AS company_name,package_name,platform,country.name AS country_name,collection.name AS collection_name,category.name AS category_name,
COUNT(package_name) AS count, AVG(application_history.ranking) AS avg
FROM application
JOIN application_history ON application_history.application_id = application.id
JOIN company ON application.company_id = company.id
JOIN country ON application_history.country_id = country.id
JOIN collection ON application_history.collection_id = collection.id
JOIN category ON application_history.category_id = category.id
WHERE application.platform=0
AND country.name ='CZ'
AND collection.name='topfreeapplications'
AND category.name='UTILITIES'
AND application_history.ranking <= 10
AND date::date BETWEEN date (CURRENT_DATE - INTERVAL '1 month') AND CURRENT_DATE
GROUP BY package_name,application.id,company.name,country.name,collection.name,category.name
ORDER BY count DESC
I think you want window/analytic functions. The following adds two columns, one for the count of rows for each package and the other an average ranking for them:
SELECT application.id, title, url, company.name AS company_name, package_name,
ranking, date, platform, country.name AS country_name,
collection.name AS collection_name, category.name AS category_name,
count(*) over (partition by package_name) as count,
avg(ranking) over (partition by package_name) as avg_package_ranking
FROM application . . .
I need to get a max of the values from two columns from different tables.
eg the max of suburbs from schoolorder and platterorder. platterorder has clientnumbers that links to normalclient, and schoolorder has clientnumbers that links to school.
I have this:
SELECT MAX (NC.SUBURB) AS SUBURB
FROM normalClient NC
WHERE NC.CLIENTNO IN
(SELECT PO.CLIENTNO
FROM platterOrder PO
WHERE NC.CLIENTNO = PO.CLIENTNO)
GROUP BY NC.SUBURB
UNION
SELECT MAX (S.SUBURB) AS SCHOOLSUBURB
FROM school S
WHERE S.CLIENTNO IN
(SELECT S.CLIENTNO
FROM schoolOrder SO
WHERE S.CLIENTNO = SO.CLIENTNO)
GROUP BY S.SUBURB)
However that gets the max from platter order and joins it with the max of school. what I need is the max of both of them together.
=================================================
sorry for making this so confusing!
the output should only be one row.
it should be the suburb where the maxmimum orders have come from for both normal client and school clients. the orders are listed in platter order for normal clients, and school order for school clients. so it's the maximum value for two table's that don't have a direct relation.
hope that clears it up a bit !
If I'm understanding your question correctly, you don't need to use a GROUP BY since you're wanting the MAX of the field. I've also changed your syntax to use a JOIN instead of IN, but the IN should work just the same:
SELECT MAX (NC.SUBURB) AS SUBURB
FROM normalClient NC
JOIN platterOrder PO ON NC.ClientNo = PO.ClientNo
UNION
SELECT MAX (S.SUBURB) AS SCHOOLSUBURB
FROM school S
JOIN schoolOrder SO ON S.CLIENTNO = SO.CLIENTNO
Withouth knowing your table structures and seeing sample data, the best way I can recommend getting the MAX of results from the UNION is to use a subquery. There may be a better way with JOINs, but it's difficult to infer from your question:
SELECT MAX(Suburb)
FROM (
SELECT MAX (NC.SUBURB) AS SUBURB
FROM normalClient NC
JOIN platterOrder PO ON NC.ClientNo = PO.ClientNo
UNION
SELECT MAX (S.SUBURB)
FROM school S
JOIN schoolOrder SO ON S.CLIENTNO = SO.CLIENTNO
) T