All i want to do is to join two tables, list ALL the rows from the first table, find the average from the second table from all the rows, then list only the ones that are greater than the average.
This is wahat i have done so far, and i am only getting one greater than the average but there are others.
SELECT winner_age, AVG(actor_age) FROM oscar_winners
INNER JOIN actors ON actors.id = oscar_winners.id
WHERE winner_age > (
SELECT AVG(actor_age)
)
You don't really need a join here:
SELECT o.WINNER_AGE
FROM OSCAR_WINNERS o
WHERE o.WINNER_AGE > (SELECT AVG(a.ACTOR_AGE)
FROM ACTORS a)
Something like this?
SELECT actors.*, (SELECT AVG(actor_age) from actors) as average
FROM oscar_winners
INNER JOIN actors ON actors.id = oscar_winners.id and actors.winner_age > (SELECT AVG(actor_age) from actors)
The problem with your query is because you are using a where clause, while you should probably be using having:
SELECT w.winner_age, AVG(a.actor_age)
FROM oscar_winners w
INNER JOIN actors a
ON actors.id = oscar_winners.id
group by w.winner_age
having w.winner_age > AVG(a.actor_age)
Related
I am using the basic chinook database and I am trying to get a query that will display the worst selling genres. I am mostly getting the answer, however there is one genre 'Opera' that has 0 sales, but the query result is ignoring that and moving on to the next lowest non-zero value.
I tried using left join instead of inner join but that returns different values.
This is my query currently:
create view max
as
select distinct
t1.name as genre,
count(*) as Sales
from
tracks t2
inner join
invoice_items t3 on t2.trackid == t3.trackid
left join
genres as t1 on t1.genreid == t2.genreid
group by
t1.genreid
order by
2
limit 10;
The result however skips past the opera value which is 0 sales. How can I include that? I tried using left join but it yields different results.
Any help is appreciated.
If you want to include genres with no sales then you should start the joins from genres and then do LEFT joins to the other tables.
Also, you should not use count(*) which counts any row in the resultset.
SELECT g.name Genre,
COUNT(i.trackid) Sales
FROM genres g
LEFT JOIN tracks t ON t.genreid = g.genreid
LEFT JOIN invoice_items i ON i.trackid = t.trackid
GROUP BY g.genreid
ORDER BY Sales LIMIT 10;
There is no need for the keyword DISTINCT, since the query returns 1 row for each genre.
When asking for the top n one must always state how to deal with ties. If I am looking for the top 1, but there are three rows in the table, all with the same value, shall I select 3 rows? Zero rows? One row arbitrarily chosen? Most often we don't want arbitrary results, which excludes the last option. This excludes LIMIT, too, because LIMIT has no clause for ties in SQLite.
Here is an example with DENSE_RANK instead. You are looking for the worst selling genres, so we must probably look at the revenue per genre, which is the sum of price x quantity sold. In order to include genres without invoices (and maybe even without tracks?) we outer join this data to the genre table.
select total, genre_name
from
(
select
g.name as genre_name,
coalesce(sum(ii.unit_price * ii.quantity), 0) as total
dense_rank() over (order by coalesce(sum(ii.unit_price * ii.quantity), 0)) as rnk
from genres g
left join tracks t on t.genreid = g.genreid
left join invoice_items ii on ii.trackid = t.trackid
group by g.name
) aggregated
where rnk <= 10
order by total, genre_name;
I am struggling with taking a Count() from one table and dividing it by a correlating number from a different table in Microsoft SQL Server.
Here is a fictional example of what I'm trying to do
Lets say I have a table of orders. One column in there is states.
I have a second table that has a column for states, and second column for each states population.
I'd like to find the order per population for each sate, but I have struggled to get my query right.
Here is what I have so far:
SELECT Orders.State, Count(*)/
(SELECT StatePopulations.Population FROM Orders INNER JOIN StatePopulations
on Orders.State = StatePopulations.State
WHERE Orders.state = StatePopulations.State )
FROM Orders INNER JOIN StatePopulations
ON Orders.state = StatePopulations.State
GROUP BY Orders.state
So far I'm contending with an error that says my sub query is returning multiple results for each state, but I'm newer to SQL and don't know how to overcome it.
If you really want a correlated sub-query, then this should do it...
(You don't need to join both table in either the inner or outer query, the correlation in the inner query's where clause does the 'join'.)
SELECT
Orders.state,
COUNT(*) / (SELECT population FROM StatePopulation WHERE state = Orders.state)
FROM
Orders
GROUP BY
Orders.state
Personally, I'd just join them and use MAX()...
SELECT
Orders.state,
COUNT(*) / MAX(StatePopulation.population)
FROM
Orders
INNER JOIN
StatePopulation
StatePopulation.state = Orders.state
GROUP BY
Orders.state
Or aggregate your orders before you join...
SELECT
Orders.state,
Orders.order_count / StatePopulation.population
FROM
(
SELECT
Orders.state,
COUNT(*) AS order_count
FROM
Orders
GROUP BY
Orders.state
)
Orders
INNER JOIN
StatePopulation
StatePopulation.state = Orders.state
(Please forgive typos and smelling pistakes, I'm doing this on a phone.)
I would like to take values from one table column and subtract those values from another column from another table.
I was able to achieve this by joining those tables and then subtracting both columns from each other.
Data from first table:
SELECT max_participants FROM courses ORDER BY id;
Data from second table:
SELECT COUNT(id) FROM participations GROUP BY course_id ORDER BY course_id;
Here is some code:
SELECT max_participants - participations AS free_places FROM
(
SELECT max_participants, COUNT(participations.id) AS participations
FROM courses
INNER JOIN participations ON participations.course_id = courses.id
GROUP BY courses.max_participants, participations.course_id
ORDER BY participations.course_id
) AS course_places;
In general, it works, but I was wondering, if there is some way to make it simplier or maybe my approach isn't correct and this code will not work in some conditions? Maybe it needs to be optimized.
I've read some information about not to rely on natural order of result set in databases and that information made my doubts to appear.
If you want the values per course, I would recommend:
SELECT c.id, (c.max_participants - COUNT(p.id)) AS free_places
FROM courses c LEFT JOIN
participations p
ON p.course_id = c.id
GROUP BY c.id, c.max_participants
ORDER BY 1;
Note the LEFT JOIN to be sure all courses are included, even those with no participants.
The overall number is a little tricker. One method is to use the above as a subquery. Alternatively, you can pre-aggregate each table:
select c.max_participants - p.num_participants
from (select sum(max_participants) as max_participants from courses) c cross join
(select count(*) as num_participants from participants from participations) p;
I have 3 Oracle tables for a project that link a demo Transaction table to Transaction_Customer and Transaction_Employee as shown below. Each transaction can have multiple customers involved and many employees involved.
I am trying to write a SQL query which will list each Customer_ID that has had transactions with multiple employees within a one period. I would like the output to include a single row for each Customer_ID with a comma separated list of which Employee_IDs had a transaction with that customer.
The output should look like this:
Customer_ID|Employees
601|007,008,009
The basic query to join the tables together looks like this:
select * from transactions t
left join transactions_customer tc
on t.t_id = tc.t_id
left join transactions_employee te
on t.t_id = te.t_id
How do I get this do I finish this assignment and get the query working the way intended?
Thank you!
Transactions
T_ID|Date|Amount
1|1/10/2017|100
2|1/10/2017|200
3|1/31/2017|150
4|2/16/2017|175
5|2/17/2017|175
6|2/18/2017|185
Transactions_Customer
T_ID|Customer_ID
1|600
1|601
1|602
2|605
3|606
4|601
5|607
6|607
Transactions_Employee
T_ID|Employee_ID
1|007
1|008
2|009
3|008
4|009
5|007
6|007
Is this what you want?
select tc.Customer_id,
listagg(te.employee_id, ',') within group (order by te.employee_id) as employees
from Transactions_Customer tc join
Transactions_Employee te
on tc.t_id = te.t_id
group by tc.Customer_id;
You only need the Transactions table for filtering on the date. Your question alludes to such filtering but does not exactly describe it, so I left it out.
Edit:
The customer data (and perhaps the employees data too) has duplicates. To avoid these in the output:
select tc.Customer_id,
listagg(te.employee_id, ',') within group (order by te.employee_id) as employees
from (select distinct tc.t_id, tc.customer_id
from Transactions_Customer tc
) tc join
(select distinct te.t_id, te.employee_id
from Transactions_Employee te
) te
on tc.t_id = te.t_id
group by tc.Customer_id;
Hi all
Im having some problems combining data from 2 tables in to 1 query.
Now I have one table-nr1 with raw data of restaurants and in the other table-nr2 I have a number of restaurants that have been graded.
So, now I want to select all restaurants and at the same time select grades of that restaurant from table-nr2 and get the average value of those grades.
How can I do this in a single SQL query?
SELECT r.*,
COALESCE(
(
SELECT AVG(grade)
FROM table_nr2 g
WHERE g.restaurant_id = r.id
), 0)
FROM table-nr1 r
Assuming your restaurants have a name and id, and the your reviews have a grade
SELECT re.name, avg(ra.grade)
FROM table-nr1 re
LEFT JOIN table-nr2 ra ON re.id = ra.id
GROUP BY re.name
You need to group by all fields you want to select which are not aggregated, and left join means you will get all restaurants, irrespective of whether they have any ratings.
You need to perform a join. In this case an inner left join sounds fine, which is the default join. You can use USING syntax if the field that links them is the same on both sides, so you would end up with something like this:
SELECT table-nr1.*, AVG(table-nr2.score)
FROM table-nr1
JOIN table-nr2 USING (restrauntId)
Otherwise you could do something that links them using an on clause like this:
SELECT table-nr1.*, AVG(table-nr2.score)
FROM table-nr1
JOIN table-nr2 ON (table-nr1.restrauntId = table-nr2.restrauntId)