How can i show which tutor teach the least subject?
this is my syntax but I'm getting
Error code 42607
select
tut_id,
min(count(session_code)) as subject_taught
from
tutor,
class
where
tutor.tutor id = class.tut_id
group by tut_id
Expected output:
tut_id subject_taught
id2 1
This is pretty simple:
WITH Subjects_Taught AS (SELECT tutor_id, COUNT(*) AS subjects_taught
FROM Class
GROUP BY tutor_id)
SELECT tutor_id, subjects_taught
FROM Subjects_Taught
WHERE subjects_taught = (SELECT MIN(subjects_taught)
FROM Subjects_Taught)
SQL Fiddle Example
So what's going on in the statement?
First, the Common Table Expression ->
WITH Subjects_Taught AS (SELECT tutor_id, COUNT(*) AS subjects_taught
FROM Class
GROUP BY tutor_id)
This defines an in-query view or temporary table. These are handy for abstracting certain details away, or when you end up referring to the same info twice in a statement (as we do here). Essentially, you end up with a table that looks like this:
id1 | 2
id2 | 1
id3 | 2
... so then the only thing left is to restrict ourselves to rows of this table that meet the minimum:
WHERE subjects_taught = (SELECT MIN(subjects_taught)
FROM Subjects_Taught)
... we reference our virtual table a second time, getting the minimum, as if it were a normal table.
I don't have a DB2 available now but as far as I can see here you cannot nest aggregate functions in DB2:
$... min(count(session_code))...
Related
Good Day,
I have 3 Tables - Ticket, Ticket Batch (Multiple Ticket Rows To One Batch) and Ticket Staff (Multiple Staff Rows To One Ticket) and wish to ultimately UPDATE the ticket_batch table with the COUNT of all staff working on tickets per ticket batch.
The tables with applicable columns look as follows
ticket:
| ticket_number | recon_number |
ticket_batch:
| recon_number |
ticket_staff:
| ticket_number |
So I have written the following SQL query to essentially first if I do get the COUNT:
SELECT COUNT(*)
FROM ticket_staf
WHERE ticket_staff.ticket_number IN (SELECT GROUP_CONCAT(ticket.ticket_number) FROM ticket WHERE ticket.recon_number = 1);
Which the query just keeps running, but when I execute the queries separately:
SELECT GROUP_CONCAT(ticket.ticket_number)
FROM ticket
WHERE ticket.recon_number = 1;
I get 5 ticket numbers within split seconds and if I paste that string in the other portion of the query:
SELECT COUNT(*)
FROM ticket_staff
WHERE ticket_staff.ticket_number IN (1451,1453,1968,4457,4458);
It returns the correct COUNT.
So ultimately I guess can I not write queries with GROUP_CONCATS into another SELECT WHERE IN? And how should I structure my query?
Thanks for reading :)
I prefer Inner join as follows:
SELECT COUNT(distinct ts.*)
FROM ticket_staff ts
LEFT JOIN ticket t
ON ts.ticket_number = t.ticket_number
WHERE t.recon_number = 1;
GROUP_CONCAT() doesn't look right. I suspect you are confusing a list of values for IN with a string. They are not the same thing.
In general, I would recommend EXISTS over IN anyway:
SELECT COUNT(*)
FROM ticket_staff ts
WHERE EXISTS (SELECT 1
FROM ticket t
WHERE ts.ticket_number = t.ticket_number AND
t.recon_number = 1
);
For this query, you want an index on ticket(ticket_number, recon_number). However, I am guessing that ticket(ticket_number) is the primary key, which is enough of an index by itself.
Despite my internet searching, I've not found a solution to what I think is a simple SQL problem.
I have a simple table as such:
zip | location | transit
------------------------
10001 | 1 | 5
10001 | 2 | 2
This table of course has a large number of zip codes, but I'd like to make s simple query by zip code and instead of returning all rows with the zip, return only a single row (with all 3 columns), that contains the lowest transit value.
I've been playing with the aggregate function min(), but haven't gotten it right.
Using Postgres SQL DB 9.6
Thanks!
Use ORDER BY along with LIMIT :
SELECT t.*
FROM mytable t
WHERE t.zipcode = ?
ORDER BY t.transit
LIMIT 1
How about
select * from table where zip = ‘10001’ order by transit limit 1
I would use distinct on:
select distinct on (zip) t.*
from t
order by zip, transit;
This is usually the most efficient method in Postgres, particularly with an index on (zip, transit).
Of course if you have only one zip code that you care about, then where/order by/limit is also totally reasonable.
Assuming that you also want to return the location value associated with the minimum transit value, then here is one possible solution using an inner join:
select t.*
from
yourtable t inner join
(select u.zip, min(u.transit) as mt from yourtable u group by u.zip) v
on t.zip = v.zip and t.transit = v.mt
Change all references to yourtable to the name of your table.
I have two tables which are joined by an ID...
table 1
- Assessment ID
- Module ID
- Assessment Weighting
table 2
- ID
- AssessmentID
- ModuleID
- UserID
- MarkFrom100
An assessment can have many students taking the assessment.
For example
A module has two assessments, one worth 60% and the other worth 40%. in table 2, I want to take the weighting value from table 1 and multiply it against the mark from 100.
SELECT * FROM Assessment, ModuleAssessmentUser WHERE
INNER JOIN moduleassementuser.assessmentID on Assessment.assessmentID
MULTIPLY AssessmentWeighting BY MarkFrom100 AS finalmark
UserID = 1
I know this is way off, but I really don't know how else to go about it.
My SQL knowledge is limited, so any help is appreciated!
You may use a SUM function in your query which will sum all the data of a certain group in a sub query wich will allow you to multiply the sum to the weight
sub query :
SELECT ModuleID, AssessmentID, UserID, SUM(MarkFrom100) as Total
FROM Table_2
GROUP BY ModuleID
Then use this sub query as a table in a main query :
SELECT T1.Assessment_ID, T1.ModuleID, Q1.UserID (Q1.Total * T1.Assessment_Weighting) as FinalMark
FROM (SELECT ModuleID, UserID, SUM(MarkFrom100) as Total
FROM Table_2
GROUP BY ModuleID) AS Q1
INNER JOIN Table_1 as T1 on T1.ModuleID = Q1.ModuleID
-- WHERE T1.ModuleID = 2 -- a particular module ID
GROUP BY ModuleID;
Note that the WHERE statement is in comment. If you want the whole data, remove it, if you want a particular data, use it ^^
NOTE :
I don't have your database, so it may need some tweeks, but the main idea is there
I need to write an sql query that will pull back the data that meets several groups of criteria from the same table. The easiest way to describe is to imagine using an SQL "in" clause but instead of the internals of that clause being "or"s joining the parameters you want it to match it is instead an "and".
I attempted to use count to verify the correct amount of data was pulled back for each "in" statement but the count can't always be trusted due to other entries being similar for each column.
A sample table might be this:
id count animal
--- ----- ------
1 5 puppy
1 6 cat
1 6 puppy
So, now I need a query that will pull back all entries with an id of 1 and a count of 5 and 6 and an animal of puppy and cat. I pretty much need to verify the entire path of the table entry to know I want to pull it back. Is there any built in function that can do this? Do I need to use a recursive CTE to dig deep after confirming that one set of criteria is met? Thanks for any help.
If I got it right
with cnt as(
select id
from tbl
where [count] in (5,6) and animal in ('puppy', 'cat')
group by id
having count(distinct[count])=2 and count(distinct animal)=2
)
select id, [count], animal
from tbl
where id in (select id from cnt);
It's kind of confusing what you're looking for exactly but can you not use or's and ands?
select id, count, animal
from table
where id = 1 and
(count = 5 or count = 6) and
(animal = puppy or anmial = cat)
I think you just want:
select t.*
from t
where id = 1 and
count in (5, 6) and
animal in ('puppy', 'cat');
EDIT:
If you want them all in the same row, just rearrange the conditions:
select t.*
from t
where id = 1 and
( (count = 5 and animal = 'puppy') or
(count = 6 and animal = 'cat')
);
I have a table that looks like this
id attribute
1 a
1 a
2 b
2 a
And I want to collect all of the IDs which have ONLY attribute a. So in the example case:
id
1
My initial thought was to use a where, but that would return:
id
1
1
2
Because 2 also has an "a" attribute in one instance.
P.S. I realize the phrasing of the title is ambiguous; maybe there's a better term than attribute to use in this case?
ohh I just saw hive but this is pretty standard sql give it a try.
SELECT
ID
FROM
TABLENAME
GROUP BY
ID
HAVING
COUNT(DISTINCT attribute) = 1
Having is like a where statement after the GROUP BY aggregation has occurred.
HiveQL equivalent of SQL using group by ,having and distinct
select id from (select id,count(distinct attribute) cnt from table_actual group by id having cnt='1') tableouter;