So i woud like to find the department name or department id(dpmid) for the group that has the max average of age among the other group and this is my query:
select
MAX(avg_age) as 'Max average age' FROM (
SELECT
AVG(userage) AS avg_age FROM user_data GROUP BY
(select dpmid from department_branch where
(select dpmbid from user_department_branch where
user_data.userid = user_department_branch.userid)=department_branch.dpmbid)
) AS query1
this code show only the max value of average age and when i try to show the name of the group it will show the wrong group name.
So, How to show the name of max group that has subquery from another table???
You may try this..
select MAX(avg_age) as max_avg, SUBSTRING_INDEX(MAX(avg_age_dep),'##',-1) as max_age_dep from
(
SELECT
AVG(userage) as avg_age, CONCAT( AVG(userage), CONCAT('##' ,department_name)) as avg_age_dep
FROM user_data
inner join user_department_branch
on user_data.userid = user_department_branch.userid
inner join department_branch
on department_branch.dpmbid = user_department_branch.dpmbid
inner join department
on department.dpmid = department_branch.dpmid
group by department_branch.dpmid
) tab_avg_age_by_dep
;
I've done some change on ipothesys that the department name is placed in a "department" anagraphical table.. so, as it needed put in join a table in plus, then I changed your query, eventually if the department name is placed (but I don't thing so) in the branch_department table you can add the field and its treatment to your query
update
In adjunct to as said, if you wanto to avoid identical average cases you can furtherly make univocal the averages by appending a rownum id in this way:
select MAX(avg_age) as max_avg, SUBSTRING_INDEX(MAX(avg_age_dep),'##',-1) as max_age_dep from
(
SELECT
AVG(userage) as avg_age, CONCAT( AVG(userage), CONCAT('##', CONCAT( #rownum:=#rownum+1, CONCAT('##' ,department_name)))) as avg_age_dep
FROM user_data
inner join user_department_branch
on user_data.userid = user_department_branch.userid
inner join department_branch
on department_branch.dpmbid = user_department_branch.dpmbid
inner join department
on department.dpmid = department_branch.dpmid
,(SELECT #rownum:=0) r
group by department_branch.dpmid
) tab_avg_age_by_dep
;
I took a shot at what I think you are looking for. The following will give you the department branch with the highest average age. I assumed the department_branch table had a department_name field. You may need an additional join to get the department.
SELECT db.department_name, udb.dpmid, AVG(userage) as `Average age`
FROM user_data as ud
JOIN user_department_branch as udb
ON udb.userid = ud.userid
JOIN department_branch as db
ON db.dpmbid = udb.dpmbid
GROUP BY udb.dpmid
ORDER BY `Average age` DESC
LIMIT 1
Related
Actually i want the data order by column name desc but its also use group by another column name ...
example:
SELECT * ,schemes.depart_id,schemes.scheme_id as s_id FROM `message_details`
left join schemes on schemes.scheme_id=message_details.scheme_id
left join department on department.id=schemes.depart_id
WHERE message_details.reciver_id=13 or message_details.sender_id=13
GROUP by message_details.scheme_id
HAVING order by message_details.msg_id desc
but result its not correct first row the not highest msg_id
SELECT * ,schemes.depart_id,schemes.scheme_id as s_id
FROM `message_details`
left join schemes on schemes.scheme_id=message_details.scheme_id
left join department on department.id=schemes.depart_id
WHERE message_details.reciver_id=13 or message_details.sender_id=13
GROUP by message_details.scheme_id
HAVING order by message_details.msg_id desc
i want the group by scheme_id with highest msg_id show in result
You seem to want filtering not aggregation.
Without sample data and desired results, it is hard to tell exactly what logic you want to implement. I suspect it is something along these lines:
select . . . -- list the columns you want here
from message_details md left join
schemes s
on s.scheme_id = md.scheme_id left join
department d
on d.id = s.depart_id
where 13 in (md.receiver_id, md.sender_id) and
md.scheme_id = (select max(md2.scheme_id)
from message_details md2
where 13 in (md2.receiver_id, md2.sender_id)
);
I have three tables in Access:
employees
----------------------------------
id (pk),name
times
----------------------
id (pk),employee_id,event_time
time_notes
----------------------
id (pk),time_id,note
I want to get the record for each employee record from the times table with an event_time immediately prior to some time. Doing that is simple enough with this:
select employees.id, employees.name,
(select top 1 times.id from times where times.employee_id=employees.id and times.event_time<=#2018-01-30 14:21:48# ORDER BY times.event_time DESC) as time_id
from employees
However, I also want to get some indication of whether there's a matching record in the time_notes table:
select employees.id, employees.name,
(select top 1 time_notes.id from time_notes where time_notes.time_id=(select top 1 times.id from times where times.employee_id=employees.id and times.event_time<=#2018-01-30 14:21:48# ORDER BY times.event_time DESC)) as time_note_present,
(select top 1 times.id from times where times.employee_id=employees.id and times.event_time<=#2018-01-30 14:21:48# ORDER BY times.event_time DESC) as last_time_id
from employees
This does work but it's SOOOOO SLOW. We're talking 10 seconds or more if there's 100 records in the employee table. The problem is peculiar to Access as I can't use the last_time_id result of the other sub-query like I can in MySQL or SQL Server.
I am looking for tips on how to speed this up. Either a different query, indexes. Something.
Not sure if something like this would work for you?
SELECT
employees.id,
employees.name,
time_notes.id AS time_note_present,
times.id AS last_time_id
FROM
(
employees LEFT JOIN
(
times INNER JOIN
(
SELECT times.employee_id AS lt_employee_id, max(times.event_time) AS lt_event_time
FROM times
WHERE times.event_time <= #2018-01-30 14:21:48#
GROUP BY times.employee_id
)
AS last_times
ON times.event_time = last_times.lt_event_time AND times.employee_id = last_times.lt_employee_id
)
ON employees.id = times.employee_id
)
LEFT JOIN time_notes ON times.id = time_notes.time_id;
(Completely untested and may contain typos)
Basically, your query is running multiple correlated subqueries even a nested one in a WHERE clause. Correlated queries calculate a value separately for each row, corresponding to outer query.
Similar to #LeeMac, simply join all your tables to an aggregate query for the max event_time grouped by employee_id which will run once across all rows. Below times is the baseFROM table joined to the aggregate query, employees, and time_notes tables:
select e.id, e.name, t.event_time, n.note
from ((times t
inner join
(select sub.employee_id, max(sub.event_time) as max_event_time
from times sub
where sub.event_time <= #2018-01-30 14:21:48#
group by sub.employee_id
) as agg_qry
on t.employee_id = agg_qry.employee_id and t.event_time = agg_qry.max_event_time)
inner join employees e
on e.id = t.employee_id)
left join time_notes n
on n.time_id = t.id
I am studying for an SQL test and the previous year has the final question:
Name the student who has studied the least number of papers. How many
papers have they studied?
So far, this is the select query that I have created:
select min(Full_Name), min(Amount)
from (select st.ST_F_Name & ' ' & st.ST_L_Name as Full_Name, count(*) as Amount
from (student_course as sc
inner join students as st
on st.ST_ID=sc.SC_ST_ID)
group by st.ST_F_Name & ' ' & st.ST_L_Name)
This works perfectly for returning the result I want but I'm not sure if this is the way I should be doing this query? I feel like calling min() on the Full_Name could potentially backfire on me under certain circumstances. Is there a better way to be doing this? (this is in MS Access for unknown reasons)
If you want only 1 of such students if there are multiple, this is probably the simplest:
select st.ST_F_Name, st.ST_L_Name, count(*) as Amount
from student_course as sc
inner join students as st
on st.ST_ID=sc.SC_ST_ID
group by st.ST_ID
order by Amount ASC LIMIT 1
However, if you want to find all stuch students, you follow a different approach. We use a WITH clause to simplify things, that defines a CTE (Common Table Expression) computing the number of courses per-student. And then we select students where their number equals to the minimum in that CTE:
with per_student as (
select st.ST_F_Name, st.ST_L_Name, count(*) as Amount
from student_course as sc
inner join students as st
on st.ST_ID=sc.SC_ST_ID
group by st.ST_ID
)
select * from per_student
where amount = (select min(amount) from per_student)
But the real trick in that question is that there might be students that didn't take ANY courses. But with approaches presented so far you'll never see them. You want something like this:
with per_student as (
select st.ST_F_Name, st.ST_L_Name, count(sc.SC_ST_ID) as Amount
from student_course as sc
right outer join students as st
on st.ST_ID=sc.SC_ST_ID
group by st.ST_ID
)
select * from per_student
where amount = (select min(amount) from per_student)
You can order by count(*) to get the student with the least # of papers:
i.e.
select * from students where st_id in (
select top 1 sc_st_id
from student_course
group by sc_st_id
order by count(*)
)
if you also need the # of papers studied, then join a derived table containing the min count:
select * from students s
left join (
select top 1 sc_st_id, count(*)
from student_course
group by sc_st_id
order by count(*)
) t on t.sc_st_id = s.st_id
I have ran a query to give me the total number of students within each school but now I need to know the name of those students within each school while keeping the top result by total number at the top. How can I add to this query to show me the names of the students?
Here is what I have to show me the total number of students at each school:
SELECT
dbo_Schools.Schools,
Count(dbo_tStudent.Student) AS NumberOfStudents
FROM
dbo_tStudent
INNER JOIN dbo_tSchools ON dbo_tStudent.SchoolID=dbo_tSchool.SchoolID
GROUP BY dbo_tSchool.School
ORDER BY Count(dbo_tStudent.Student) DESC;
Its important that I keep the schools in order from top number of students while listing the students
In this case you could use a Sub Query to achieve your resultset.
To use order by inside a subquery, you will also need a top or limit operator.
SELECT sc.schoolname
,st.columns...
FROM dbo_tStudent st
INNER JOIN (
SELECT TOP 1000 dbo_Schools.SchoolID
,min(schoolname) schoolname
,Count(dbo_tStudent.Student) AS NumberOfStudents
FROM dbo_tStudent
INNER JOIN dbo_tSchools ON dbo_tStudent.SchoolID = dbo_tSchools.SchoolID
GROUP BY dbo_tSchool.School
ORDER BY Count(dbo_tStudent.Student) DESC
) sc ON st.SchoolID = sc.SchoolID
Assuming that you are using SQL Server, you can use a CTE to join the first aggregate with the details like this:
;WITH cte as (
SELECT TOP 1000 dbo_Schools.SchoolID, Count(dbo_tStudent.Student) AS NumberOfStudents
FROM
dbo_tStudent
INNER JOIN dbo_tSchools ON dbo_tStudent.SchoolID = dbo_tSchools.SchoolID
GROUP BY dbo_tSchool.School
ORDER BY Count(dbo_tStudent.Student) DESC
)
SELECT
sc.<your school name column>,
st.<your student columns>
from
dbo_tStudent st
INNER JOIN cte ON st.SchoolID = cte.SchoolID
INNER JOIN dbo_tSchools sc on cte.SchoolID = sc.SchoolID
More generally speaking: you need a derived table (your aggregation containing the group by clause) that is joined with the select statement for the student details. In this example, the CTE basically is a SQL Server feature that facilitates the use of derived tables.
I asked this question on SO. However, I wish to extend it further. I would like to find the max value of the 'Reading' column only where the 'state' is of value 'XX' for example.
So if I join the two tables, how do I get the row with max(Reading) value from the result set. Eg.
SELECT s.*, g1.*
FROM Schools AS s
JOIN Grades AS g1 ON g1.id_schools = s.id
WHERE s.state = 'SA' // how do I get row with max(Reading) column from this result set
The table details are:
Table1 = Schools
Columns: id(PK), state(nvchar(100)), schoolname
Table2 = Grades
Columns: id(PK), id_schools(FK), Year, Reading, Writing...
I'd think about using a common table expression:
WITH SchoolsInState (id, state, schoolname)
AS (
SELECT id, state, schoolname
FROM Schools
WHERE state = 'XX'
)
SELECT *
FROM SchoolsInState AS s
JOIN Grades AS g
ON s.id = g.id_schools
WHERE g.Reading = max(g.Reading)
The nice thing about this is that it creates this SchoolsInState pseudo-table which wraps all the logic about filtering by state, leaving you free to write the rest of your query without having to think about it.
I'm guessing [Reading] is some form of numeric value.
SELECT TOP (1)
s.[Id],
s.[State],
s.[SchoolName],
MAX(g.[Reading]) Reading
FROM
[Schools] s
JOIN [Grades] g on g.[id_schools] = s.[Id]
WHERE s.[State] = 'SA'
Group By
s.[Id],
s.[State],
s.[SchoolName]
Order By
MAX(g.[Reading]) DESC
UPDATE:
Looking at Tom's i don't think that would work but here is a modified version that does.
WITH [HighestGrade] (Reading)
AS (
SELECT
MAX([Reading]) Reading
FROM
[Grades]
)
SELECT
s.*,
g.*
FROM
[HighestGrade] hg
JOIN [Grades] AS g ON g.[Reading] = hg.[Reading]
JOIN [Schools] AS s ON s.[id] = g.[id_schools]
WHERE s.state = 'SA'
This CTE method should give you what you want. I also had it break down by year (grade_year in my code to avoid the reserved word). You should be able to remove that easily enough if you want to. This method also accounts for ties (you'll get both rows back if there is a tie):
;WITH MaxReadingByStateYear AS (
SELECT
S.id,
S.school_name,
S.state,
G.grade_year,
RANK() OVER(PARTITION BY S.state, G.grade_year ORDER BY Reading DESC) AS ranking
FROM
dbo.Grades G
INNER JOIN Schools S ON
S.id = G.id_schools
)
SELECT
id,
state,
school_name,
grade_year
FROM
MaxReadingByStateYear
WHERE
state = 'AL' AND
ranking = 1
One way would be this:
SELECT...
FROM...
WHERE...
AND g1.Reading = (select max(G2.Reading)
from Grades G2
inner join Schools s2
on s2.id = g2.id_schools
and s2.state = s.state)
There are certainly more.