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)
Related
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)
I need to write SQL query like:
Show all countries with more than 1000 users, sorted by user count.
The country with the most users should be at the top.
I have tables:
● Table users (id, email, citizenship_country_id)
● Table countries (id, name, iso)
Users with columns: id, email, citizenship_country_id
Countries with columns: id, name, iso
SELECT countries.name,
Count(users.citiizenship_country_id) AS W1
FROM countries
LEFT JOIN users ON countries.id = users.citizenship_country_id
GROUP BY users.citiizenship_country_id, countries.name
HAVING ((([users].[citiizenship_country_id])>2));
But this does not work - I get an empty result set.
Could you please tell me what I'm doing wrong?
A LEFT JOIN is superfluous for this purpose. To have 1000 users, you need at least one match:
SELECT c.name, Count(*) AS W1
FROM countries c JOIN
users u
ON c.id = u.citizenship_country_id
GROUP BY c.name
HAVING COUNT(*) > 1000;
Notice that table aliases also make the query easier to write and to read.
Group by country name and use HAVING Count(u.citiizenship_country_id)>1000, it filters rows after aggregation:
SELECT c.name,
Count(u.citiizenship_country_id) AS W1
FROM countries c
INNER JOIN users u ON c.id = u.citizenship_country_id
GROUP BY c.name
HAVING Count(u.citiizenship_country_id)>1000
ORDER BY W1 desc --Order top counts first
;
As #GordonLinoff pointed, you can use INNER JOIN instead of LEFT JOIN, because anyway this query does not return counries without users and INNER JOIN performs better because no need to pass not joined records to the aggregation.
i have following sql in java project:
select distinct * from drivers inner join licenses on drivers.user_id=licenses.issuer_id
inner join users on drivers.user_id=users.id
where (licenses.state='ISSUED' or drivers.status='WAITING')
and users.is_deleted=false
And result i database looks like this:
And i would like to get only one result instead of two duplicated results.
How can i do that?
Solution 1 - That's Because one of data has duplicate value write distinct keyword with only column you want like this
Select distinct id, distinct creation_date, distinct modification_date from
YourTable
Solution 2 - apply distinct only on ID and once you get id you can get all data using in query
select * from yourtable where id in (select distinct id from drivers inner join
licenses
on drivers.user_id=licenses.issuer_id
inner join users on drivers.user_id=users.id
where (licenses.state='ISSUED' or drivers.status='WAITING')
and users.is_deleted=false )
Enum fields name on select, using COALESCE for fields which value is null.
usually you dont query distinct with * (all columns), because it means if one column has the same value but the rest isn't, it will be treated as a different rows. so you have to distinct only the column you want to, then get the data
I suspect that you want left joins like this:
select *
from users u left join
drivers d
on d.user_id = u.id and d.status = 'WAITING' left join
licenses l
on d.user_id = l.issuer_id and l.state = 'ISSUED'
where u.is_deleted = false and
(d.user_id is not null or l.issuer_id is not null);
I have this simple unioned query in SQL Server 2014 where I am getting counts of rows from each table, and then trying to add a TOTAL row at the bottom that will SUM the counts from both tables. I believe the problem is the LEFT OUTER JOIN on the last union seems to be only summing the totals from the first table
SELECT A.TEST_CODE, B.DIVISION, COUNT(*)
FROM ALL_USERS B, SIGMA_TEST A
WHERE B.DOMID = A.DOMID
GROUP BY A.TEST_CODE, B.DIVISION
UNION
SELECT E.TEST_CODE, F.DIVISION, COUNT(*)
FROM BETA_TEST E, ALL_USERS F
WHERE E.DOMID = F.DOMID
GROUP BY E.TEST_CODE, F.DIVISION
UNION
SELECT 'TOTAL', '', COUNT(*)
FROM (SIGMA_TEST A LEFT OUTER JOIN BETA_TEST E ON A.DOMID
= E.DOMID )
Here is a sample of the results I am getting:
I would expect the TOTAL row to display a result of 6 (2+1+3=6)
I would like to avoid using a Common Table Expression (CTE) if possible. Thanks in advance!
Since you are counting users with matching DOMIDs in the first two statements, the final statement also needs to include the ALL_USERS table. The final statement should be:
SELECT 'TOTAL', '', COUNT(*)
FROM ALL_USERS G LEFT OUTER JOIN
SIGMA_TEST H ON G.DOMID = H.DOMID
LEFT OUTER JOIN BETA_TEST I ON I.DOMID = G.DOMID
WHERE (H.TEST_CODE IS NOT NULL OR I.TEST_CODE IS NOT NULL)
I would consider doing a UNION ALL first then COUNT:
SELECT COALESCE(TEST_CODE, 'TOTAL'),
DIVISION,
COUNT(*)
FROM (
SELECT A.TEST_CODE, B.DIVISION
FROM ALL_USERS B
INNER JOIN SIGMA_TEST A ON B.DOMID = A.DOMID
UNION ALL
SELECT E.TEST_CODE, F.DIVISION
FROM BETA_TEST E
INNER JOIN ALL_USERS F ON E.DOMID = F.DOMID ) AS T
GROUP BY GROUPING SETS ((TEST_CODE, DIVISION ), ())
Using GROUPING SETS you can easily get the total, so there is no need to add a third subquery.
Note: I assume you want just one count per (TEST_CODE, DIVISION). Otherwise you have to also group on the source table as well, as in #Gareth's answer.
I think you can achieve this with a single query. It seems your test tables have similar structures, so you can union them together and join to ALL_USERS, finally, you can use GROUPING SETS to get the total
SELECT ISNULL(T.TEST_CODE, 'TOTAL') AS TEST_CODE,
ISNULL(U.DIVISION, '') AS DIVISION,
COUNT(*)
FROM ALL_USERS AS U
INNER JOIN
( SELECT DOMID, TEST_CODE, 'SIGNMA' AS SOURCETABLE
FROM SIGMA_TEST
UNION ALL
SELECT DOMID, TEST_CODE, 'BETA' AS SOURCETABLE
FROM BETA_TEST
) AS T
ON T.DOMID = U.DOMID
GROUP BY GROUPING SETS ((T.TEST_CODE, U.DIVISION, T.SOURCETABLE), ());
As an aside, the implicit join syntax you are using was replaced over a quarter of a century ago in ANSI 92. It is not wrong, but there seems to be little reason to continue to use it, especially when you are mixing and matching with explicit outer joins and implicit inner joins. Anyone else that might read your SQL will certainly appreciate consistency.
I'm writing a query to multiply the count that I receive from subquery to fees amount, But I don't know how to do that. Any help/suggestion?
Oracle query is:
select courseid,coursename,fees*tmp
from course c join registration r on
r.courseid=c.courseid
and tmp IN (select count(*)
from course c join registration r on
r.courseid=c.courseid group by coursename);
I tried to use like a variable tmp ,But i don't think it works in oracle query. Is there an alternative way to do so?
You can't do that, because you can only select data from tables that appeared between FROM and WHERE. The IN operator is a quick way to save having to write a bunch of OR statements, it is not something that can establish a variable in the outer query.
Instead do something like:
select courseid,coursename,fees * COUNT(r.courseID) OVER(PARTITION BY c.coursename)
from course c join registration r on
r.courseid=c.courseid
Edit/update: you noted that this query produces too many rows and you only want to see distinct course names. In that case it would be better to just use the registrations table to count the number of people on the course and then multiply the fees:
SELECT
c.courseid, c.coursename, c.fees * COALESCE(r.numberOfstudents, 0) as courseWorth
FROM
course c
LEFT OUTER JOIN
(select courseid, COUNT(*) as numberofstudents FROM registration GROUP BY courseid) r
ON c.courseID = r.courseid
You can use a windowing function like Caius or you can use a join like this:
select courseid,coursename, fees * COALESCE(sub.cnt,0)
from course c
join registration r on r.courseid=c.courseid
left join (
select coursename, count(*) as cnt
from course c2
join registration r2 on r2.courseid=c2.courseid
group by coursename
) as sub;
note: I make no claim your joins are correct -- I'm basing this query off of your example not on any knowledge of your data model.