My expected output:
And I write like below:
SELECT c.cID, s.svcID, s.svcNote
FROM company c
LEFT JOIN service s ON s.cID = c.cID
LEFT JOIN (SELECT MAX(s.svcID) AS svcID
FROM service s
GROUP BY s.cID) AS s1 ON s1.svcID = s.svcID
ORDER BY c.cJoinDate DESC
However, I can't get my expected output and taking very long time to run my query. Can someone help me?
Since you want only those entries with service, you need to use INNER JOIN instead of LEFT JOIN. LEFT JOIN will list all records in Company, including cID = 4.
Try this instead:
SELECT c.cID, s.svcID, s.svcNote
FROM company c
INNER JOIN service s ON s.cID = c.cID
WHERE s.ID = (SELECT MAX(s2.svcID)
FROM service s2
WHERE s1.svcID = s2.svcID
GROUP BY s2.cID)
ORDER BY c.cJoinDate DESC
SELECT c.cID, MAX(s.svcID), s.svcNote
FROM company c
INNER JOIN service s ON s.cID = c.cID
GROUP BY s.cID
ORDER BY c.cJoinDate DESC
Related
I tried to answer this question here in the code below, but it keeps giving me an error message!
I've tried to figure out how to
Provide the name of the sales_rep in each region with the largest amount of total_amt_usd sales?
and it gave me this Error :
aggregate function calls cannot be nested
ERD picture here
could you please help me with this?
WITH
account_info AS (Select * from accounts),
orders_info AS (select * from orders),
region_info AS (select * from region),
sales_reps_info AS (select * from sales_reps)
SELECT s.name as rep_name, r.name as region_name, MAX (SUM (o.total_amt_usd)) as total
FROM orders_info o
JOIN account_info a
ON o.account_id = a.id
JOIN sales_reps_info s
ON a.sales_rep_id = s.id
JOIN region_info r
ON r.id = s.region_id
GROUP BY TOTAL, REP_NAME, R.NAME
ORDER BY 3 DESC
When you are using the whole table there is no need for WITH
SELECT s.name as rep_name, r.name as region_name, MAX (SUM (o.total_amt_usd)) as total
FROM orders o
JOIN account a
ON o.account_id = a.id
JOIN sales_reps s
ON a.sales_rep_id = s.id
JOIN region r
ON r.id = s.region_id
GROUP BY TOTAL, REP_NAME, R.NAME
ORDER BY 3 DESC
LIMIT 100;
I'm not sure what you are attempting with with since you don't actually define a Common Table Expression.
That aside, your query is invalid, you cannot nest aggregate functions and you are already getting the max 100 by ordering and limiting rows, so I think you just want
SELECT s.name as rep_name, r.name as region_name, SUM (o.total_amt_usd) as Total
FROM orders_info o
JOIN account_info a ON o.account_id = a.id
JOIN sales_reps_info s ON a.sales_rep_id = s.id
JOIN region_info r ON r.id = s.region_id
GROUP BY REP_NAME, R.NAME
ORDER BY Total DESC
LIMIT 100;
I'm working with the Sakila sample database, and trying to get the most viewed film per country. So far I've managed to get the most viewed film of a certain country given its id with the following query:
SELECT
F.title, CO.country, count(F.film_id) as times
FROM
customer C
INNER JOIN
address A ON C.address_id = A.address_id
INNER JOIN
city CI ON A.city_id = CI.city_id
INNER JOIN
country CO ON CI.country_id = CO.country_id
INNER JOIN
rental R ON C.customer_id = R.customer_id
INNER JOIN
inventory I ON R.inventory_id = I.inventory_id
INNER JOIN
film F ON I.film_id = F.film_id
WHERE
CO.country_id = 1
GROUP BY
F.film_id
ORDER BY
times DESC
LIMIT 1;
I supose that I'll have to use this query or something similar in the FORM of another query, but I've tried it all I could think and am completely unable to figure out how to do so.
Thanks in advance!
I admit, this is a hell of a query. But well, as long as it works.
Explanation:
Subquery: almost the same as you already has. Without the WHERE and LIMIT. Resulting in a list of movie-count per country
Result of that, grouped per country
GROUP_CONCAT(title ORDER BY times DESC SEPARATOR '|||'), will give ALL titles in that 'row', with the most-viewed title first. The separator doesn't matter, as long as you are sure it will never occurs in a title.
SUBSTRING_INDEX('...', '|||', 1) results in the first part of the string until it finds |||, in this case the first (and thus most-viewed) title
Full query:
SELECT
country_name,
SUBSTRING_INDEX(
GROUP_CONCAT(title ORDER BY times DESC SEPARATOR '|||'),
'|||', 1
) as title,
MAX(times)
FROM (
SELECT
F.title AS title,
CO.country_id AS country_id,
CO.country AS country_name,
count(F.film_id) as times
FROM customer C INNER JOIN address A ON C.address_id = A.address_id
INNER JOIN city CI ON A.city_id = CI.city_id
INNER JOIN country CO ON CI.country_id = CO.country_id
INNER JOIN rental R ON C.customer_id = R.customer_id
INNER JOIN inventory I ON R.inventory_id = I.inventory_id
INNER JOIN film F ON I.film_id = F.film_id
GROUP BY F.film_id, CO.country_id
) AS count_per_movie_per_country
GROUP BY country_id
Proof of concept (as long as the subquery is correct): SQLFiddle
I have a database with the tables:
Student(SID,Name,Surname,Age)
Registration(StudentID,CourseID)
Course(CID,Name,Cost)
I would like to extract only the name of the courses with students younger than 20. Will the query below do just that?
SELECT C.NAME
FROM Course C
INNER JOIN Registration
INNER JOIN Student S
WHERE CID = CourseID
AND SID = StudentID
AND Age < 20
GROUP BY C.NAME
I would also like to extract the number of students in each course having students younger than 20. Is it correct to do it as below?
SELECT count(S.NAME)
,C.NAME
FROM Student S
INNER JOIN Course C
INNER JOIN Registration
WHERE Age < 20
AND CID = CourseID
AND SID = StudentID
GROUP BY C.NAME
You are missing the ON part for the join otherwise it would just be a CROSS JOIN.
Your first query should look like this if you want just a distinct list of student names:
SELECT DISTINCT C.NAME
FROM Course C
INNER JOIN Registration R ON C.CID = R.CourseID
INNER JOIN Student S ON R.StudentID = S.SID
WHERE Age < 20
Your second query shouldn't really have the C.Name in the select if you want to get just a count unless you want a count of how many students have that name.
SELECT count(*)
FROM Student S
INNER JOIN Registration R ON s.SID = R.StudentID
INNER JOIN Course C ON c.CID = R.CourseID
WHERE Age < 20
GROUP BY C.NAME
First join these tables, then group by Course's PK(CID), Add the HAVING condition to filter the course which has students younger than 20.
Then use Course table to join the result to get the course name and count of students in the course.
SELECT
T1.Name,
T2.StudentCount
FROM
Course T1
INNER JOIN (
SELECT
c.CID,
COUNT(s.SID) AS StudentCount
FROM
Course c
LEFT JOIN Registration r ON c.CID = r.CourseID
LEFT JOIN Student s ON s.SID = r.StudentID
GROUP BY c.CID
HAVING COUNT(IF(s.Age < 20, 1, NULL)) > 0
) T2 ON T1.CID = T2.CID
More correctly, you should move the conditions of the join, to the join statements themselves by including them in the on clause instead of the where. While the results may not change in this instance, if you were to start including outer joins you would encounter difficulties.
SELECT count(S.NAME)
,C.NAME
FROM Student S
INNER JOIN Registration R
ON s.SID = R.StudentID
INNER JOIN Course C
ON c.CID = R.CourseID
WHERE Age < 20
GROUP BY C.NAME
There's a fiddle here showing it in action: http://sqlfiddle.com/#!9/c3b8f/1
Your first query will also produce the results you want, but again, you should move the join predicates to the join itself. Also, you don't need to perform the grouping just to get distinct values, mysql has an expression for that called distinct. So rewritten, the first query would look like:
SELECT DISTINCT C.NAME
FROM Student S
INNER JOIN Registration R
ON s.SID = R.StudentID
INNER JOIN Course C
ON c.CID = R.CourseID
WHERE Age < 20.
Again, the results are the same as what you have already but it is easier to 'read' and will put you in good stead when you move on to other queries. As it stands you have mixed implicit and explicit join syntax.
This fiddle demonstrates both queries: http://sqlfiddle.com/#!9/c3b8f/4
edit
I may have misinterpreted your original question - if you want the total number of students enrolled in a course with at least one student under 19, you can use a query like this:
select name, count(*)
from course c
inner join registration r
on c.cid = r.courseid
where exists (
select 1
from course cc
inner join registration r
on cc.cid = r.courseid
inner join student s
on s.sid = r.studentid
where cc.cid = c.cid
group by cc.cid
having min(s.age) < 20
)
group by name;
Again with the updated fiddle here: http://sqlfiddle.com/#!9/c3b8f/17
I have three tables, libraryitems, copies and loans.
A libraryitem hasMany copies, and a copy hasMany loans.
I'm trying to get the latest loan entry for a copy only; The query below returns all loans for a given copy.
SELECT
libraryitems.title,
copies.id,
copies.qruuid,
loans.id AS loanid,
loans.status,
loans.byname,
loans.byemail,
loans.createdAt
FROM copies
INNER JOIN libraryitems ON copies.libraryitemid = libraryitems.id AND libraryitems.deletedAt IS NULL
LEFT OUTER JOIN loans ON copies.id = loans.copyid
WHERE copies.libraryitemid = 1
ORDER BY copies.id ASC, loans.createdAt DESC
I know there needs to be a sub select of some description in here, but struggling to get the correct syntax. How do I only return the latest, i.e MAX(loans.createdAt) row for each distinct copy? Just using group by copies.id returns the earliest, rather than latest entry.
Image example below:
in the subquery , getting maximum created time for a loan i.e. latest entry and joining back with loans to get other details.
SELECT
T.title,
T.id,
T.qruuid,
loans.id AS loanid,
loans.status,
loans.byname,
loans.byemail,
loans.createdAt
FROM
(
SELECT C.id, C.qruuid, L.title, MAX(LN.createdAt) as maxCreatedTime
FROM Copies C
INNER JOIN libraryitems L ON C.libraryitemid = L.id
AND L.deletedAt IS NULL
LEFT OUTER JOIN loans LN ON C.id = LN.copyid
GROUP BY C.id, C.qruuid, L.title) T
JOIN loans ON T.id = loans.copyid
AND T.maxCreatedTime = loans.createdAt
A self left join on loans table will give you latest loan of a copy, you may join the query to the other tables to fetch the desired output.
select * from loans A
left outer join loans B
on A.copyid = B.copyid and A.createdAt < B.createdAt
where B.createdAt is null;
This is your query with one simple modification -- table aliases to make it clearer.
SELECT li.title, c.id, c.qruuid,
l.id AS loanid, l.status, l.byname, l.byemail, l.createdAt
FROM copies c INNER JOIN
libraryitems li
ON c.libraryitemid = li.id AND
li.deletedAt IS NULL LEFT JOIN
loans l
ON c.id = l.copyid
WHERE c.libraryitemid = 1
ORDER BY c.id ASC, l.createdAt DESC ;
With this as a beginning let's think about what you need. You want the load with the latest createdAt date for each c.id. You can get this information with a subquery:
select l.copyid, max(createdAt)
from loans
group by l.copyId
Now, you just need to join this information back in:
SELECT li.title, c.id, c.qruuid,
l.id AS loanid, l.status, l.byname, l.byemail, l.createdAt
FROM copies c INNER JOIN
libraryitems li
ON c.libraryitemid = li.id AND
li.deletedAt IS NULL LEFT JOIN
loans l
ON c.id = l.copyid LEFT JOIN
(SELECT l.copyid, max(l.createdAt) as maxca
FROM loans
GROUP BY l.copyid
) lmax
ON l.copyId = lmax.copyId and l.createdAt = lmax.maxca
WHERE c.libraryitemid = 1
ORDER BY c.id ASC, l.createdAt DESC ;
This should give you the most recent record. And, the use of left join should keep all copies, even those that have never been leant.
I have two tables 1 and 2 or i need this result (see my image 1) using Join in mysql also see my Query for verification
SELECT c.`id`,
c.`name`,
COUNT(*) AS `totalcount`
FROM categories c INNER JOIN subcategories sc
ON c.`id` = sc.`cat_id`
GROUP BY c.`id`
ORDER BY c.added_date DESC
I want this result
Table 1
Table 2
Help are definitely appreciated
USE LEFT JOIN instead of INNER JOIN
try this:
SELECT a.`id`, a.`name`, count(b.`cat_id`) as totalCount
FROM categories a LEFT JOIN subcategories b
on a.id = b.cat_ID
GROUP BY a.`id`
ORDER BY a.added_date desc
Use LEFT JOIN instead of INNER JOIN -
SELECT c.`id`, c.`name`,
COUNT(sc.cat_id) AS `totalcount`
FROM categories c LEFT JOIN
subcategories sc
ON c.`id` = sc.`cat_id`
GROUP BY c.`id`
ORDER BY c.added_date DESC;
A demo is here.