COUNT and DISTINCT without group by - mariadb

I've two tables. One with clients, other with products bought by clients.
When I want to get the list of all products and clients, I do:
SELECT client_name, prod_id FROM TAB_CLIENT
INNER JOIN TAB_PROD ON prod_client = client_name
So I get (eg)
Henri - Potatoes
Henri - Chocolate
Tom - Beer
Nice. Now I want to know how many different clients I have.
So I tried to use COUNT and DISTINCT. Like this:
SELECT COUNT(DISTINCT client_name) AS num_client, client_name, prod_id
FROM TAB_CLIENT
INNER JOIN TAB_PROD ON prod_client = client_name
I want to get:
2 - Henri - Potatoes
2 - Henri - Chocolate
2 - Tom - Beer
So "2" in first colum as the whole number of different clients is 2 (Henri and Tom), name of the client at second colum and name of product as third colume.
But in fact if I add the count(distinct), I get only ONE result (seems like if there was a "group by" on num_client). And I don't want to GROUP BY on client_name as in this case I'll loose the product.
Is it possible to perform that in one query, or do I have to perform one select for counting and an other to get the result?
I notice all examples given in Stack are about Count/Distinct returning only number but not the number AND results.
Thanks
PS: I'm running MariaDB.

SELECT
( SELECT COUNT(DISTINCT client_name) FROM TAB_CLIENT ) AS Number_of_clients,
client_name,
prod_id
FROM TAB_CLIENT
INNER JOIN TAB_PROD ON prod_client = client_name

Related

Would these two SQLite queries generate the same result?

I'm working through this exercise.
On question 4, the goal is to find employees hired after "Jones". I think this problem can be solved without a join like so:
SELECT first_name, last_name, hire_date
FROM employees
WHERE hire_date > (
SELECT hire_date FROM employees WHERE last_name = "Jones"
)
But the answer on the website suggests:
SELECT e.first_name, e.last_name, e.hire_date
FROM employees e
JOIN employees davies
ON (davies.last_name = "Jones")
WHERE davies.hire_date < e.hire_date;
Are these more-or-less the same or is there a reason the second answer should be considered better?
I assume that the column last_name is defined as UNIQUE, so that the subquery in the 1st query returns only 1 row.
If not, then the queries do not return the same results, because although the subquery in the 1st query may return more than 1 row (and in other databases the query would not even run), SQLite will pick just the 1st of the returned rows and use its hire_date to compare it with all the rows of the table, while the join will use all the rows where last_name = "Jones".
If my assumption is correct then the 2 queries are equivalent, but the 1st one is what I would suggest because it is more readable and I believe it would perform better than the join.
If I had to use a join for this requirement (since it is homework) I would choose a more readable form:
SELECT e.first_name, e.last_name, e.hire_date
FROM employees e
JOIN (SELECT * FROM employees WHERE last_name = "Jones") t
ON t.hire_date < e.hire_date;

More than one result on request with limit 1 sqllite

The result is one line, but there are several people with the same value of the bonus field
SELECT Name, bonus
From employees
ORDER by bonus
Limit 1
result
Ivan 100
but it is required that it was
Ivan 100
Petr 100
did this, but it seems very confusing to me:
SELECT Name, bonus
From employees
Where bonus= (SELECT id From employees ORDER by bonus Limit 1)
In SQLite you can achieve that by using RANK or dense_rank window function
select name, bonus
from (select name, bonus, dense_rank() over(order by bonus desc) dns_rnk from employees)
where dns_rnk = 1;
In sub-query it will rank employees on bonus and the outer query will filter out unneeded lines.

I've got 2 questions regarding sqlite3 queries using 2 tables

A) List each lecturer together with each module they teach and the number of students studying that module, in order of the lecturer name.
B) Output the number of modules in which everyone passed the module (assuming pass mark is 40).
For A, you need to join the 2 tables and then group by lecturer, module and count the number of rows for each group (each row corresponds to a student):
select t.lecturer, t.module, count(*) numberofstudents
from teaches t inner join studies s
on s.module = t.module
group by t.lecturer, t.module
order by t.lecturer
For B, use NOT EXISTS to find the modules where all grades are >= 40 and count them:
select count(distinct module) numberofmodules
from studies s
where not exists (
select 1 from studies
where module = s.module and grade < 40
)

How to get the total quantity of results using count(*)?

i need to get the total quantity of results for each person but i get ...
resultado
MY QUERY..
select t.fecha_hora_timbre,e.nombre,e.apellido,d.descripcion as departamento_trabaja, t.fecha,count(*)
from fulltime.timbre t, fulltime.empleado e, fulltime.departamento d
where d.depa_id=e.depa_id and t.codigo_empleado=e.codigo_empleado and
trunc(t.fecha) between trunc(to_date('15/02/2017','dd/mm/yyyy')) and trunc(to_date('14/03/2017','dd/mm/yyyy'))
group by t.fecha_hora_timbre,e.nombre,e.apellido,d.descripcion, t.fecha
Expected data...
NOMBRE | APELLIDO | DEPARTAMENTO_TRABAJA | VECES_MARCADAS(count)
MARIA TARCILA IGLESIAS BECERRA ALCALDIA 4
KATHERINE TATIANA SEGOVIA FERNANDEZ ALCALDIA 10
FREDDY AGUSTIN VALDIVIESO VALLEJO ALCALDIA 3
UPDATE..
select e.nombre,e.apellido,d.descripcion as departamento_trabaja,COUNT(*)
from fulltime.timbre t, fulltime.empleado e, fulltime.departamento d
where d.depa_id=e.depa_id and t.codigo_empleado=e.codigo_empleado and
trunc(t.fecha) between trunc(to_date('15/02/2017','dd/mm/yyyy')) and trunc(to_date('14/03/2017','dd/mm/yyyy'))
group by t.fecha_hora_timbre,e.nombre,e.apellido,d.descripcion, t.fecha
You should only select and group by the non-aggregate columns you actually want to count against. At the moment you're including the fecha_hora_timbre and fechacolumns in each row, so you're counting the unique combinations of those columns as well as the name/department information you actually want to count.
select e.nombre, e.apellido, d.descripcion as departamento_trabaja,
count(*) a veces_marcadas
from fulltime.timbre t
join fulltime.empleado e on t.codigo_empleado=e.codigo_empleado
join fulltime.departamento d on d.depa_id=e.depa_id
where t.fecha >= to_date('15/02/2017','dd/mm/yyyy')
and t.fecha < to_date('15/03/2017','dd/mm/yyyy')
group by e.nombre, e.apellido, d.descripcion
I've removed the extra columns. Notice that they have gone from both the select list and the group-by clause. If you have a non-aggregate column in the select list that isn't in the group-by you'll get an ORA-00937 error; but if you have a column in the group-by that isn't in the select list then it will still group by that even though you can't see it and you just won't get the results you expect.
I've also changed from old-style join syntax to modern syntax. And I've changed the date comparison; firstly because doing trunc() as part of trunc(to_date('15/02/2017','dd/mm/yyyy')) is pointless - you already know the time part is midnight, so the trunc doesn't achieve anything. But mostly so that if there is an index on fecha that index can be used. If you do trunc(f.techa) then the value of every column value has to be truncated, which stops the index being used (unless you have a function-based index). As between in inclusive, using >= and < with one day later on the higher limit should have the same effect overall.

Cognos: Count the number of occurences of a distinct id

I'm making a report in Cognos Report Studio and I'm having abit of trouble getting a count taht I need. What I need to do is count the number of IDs for a department. But I need to split the count between initiated and completed. If an ID occures more than once, it is to be counted as completed. The others, of course, will be initiated. So I'm trying to count the number of ID occurences for a distinct ID. Here is the query I've made in SQl Developer:
SELECT
COUNT((CASE WHEN COUNT(S.RFP_ID) > 8 THEN MAX(CT.GCT_STATUS_HISTORY_CLOSE_DT) END)) AS "Sales Admin Completed"
,COUNT((CASE WHEN COUNT(S.RFP_ID) = 8 THEN MIN(CT.GCT_STATUS_HISTORY_OPEN_DT) END)) as "Sales Admin Initiated"
FROM
ADM.B_RFP_WC_COVERAGE_DIM S
JOIN ADM.B_GROUP_CHANGE_REQUEST_DIM CR
ON S. RFP_ID = CR.GCR_RFP_ID
JOIN ADM.GROUP_CHANGE_TASK_FACT CT
ON CR.GROUP_CHANGE_REQUEST_KEY = CT.GROUP_CHANGE_REQUEST_KEY
JOIN ADM.B_DEPARTMENT_DIM D
ON D.DEPARTMENT_KEY = CT.DEPARTMENT_RESP_KEY
WHERE CR.GCR_CHANGE_TYPE_ID = '20'
AND S.RFP_LOB_IND = 'WC'
AND S.RFP_AUDIT_IND = 'N'
AND CR.GCR_RECEIVED_DT BETWEEN '01-JAN-13' AND '31-DEC-13'
AND D.DEPARTMENT_DESC = 'Sales'
AND CT.GCT_STATUS_IND = 'C'
GROUP BY S.RFP_ID ;
Now this works. But I'm not sure how to translate taht into Cognos. I tried doing a CASE taht looked liek this(this code is using basic names such as dept instead of D.DEPARTMENT_DESC):
CASE WHEN dept = 'Sales' AND count(ID for {DISTINCT ID}) > 1 THEN count(distinct ID)END)
I'm using count(distinct ID) instead of count(maximum(close_date)). But the results would be the same anyway. The "AND" is where I think its being lost. It obviously isn't the proper way to count occurences. But I'm hoping I'm close. Is there a way to do this with a CASE? Or at all?
--EDIT--
To make my question more clear, here is an example:
Say I have this data in my table
ID
---
1
2
3
4
2
5
5
6
2
My desired count output would be:
Initiated Completed
--------- ---------
4 2
This is because two of the distinct IDs (2 and 5) occure more than once. So they are counted as Completed. The ones that occure only once are counted as Initiated. I am able to do this in SQl Dev, but I can't figure out how to do this in Cognos Report Studio. I hope this helps to better explaine my issue.
Oh, I didn't quite got it originally, amending the answer.
But it's still easiest to do with 2 queries in Report Studio. Key moment is that you can use a query as a source for another query, guaranteeing proper group by's and calculations.
So if you have ID list in the table in Report Studio you create:
Query 1 with dataitems:
ID,
count(*) or count (1) as count_occurences
status (initiated or completed) with a formula: if (count_occurences > 1) then ('completed') else ('initiated').
After that you create a query 2 using query one as source with just 2 data items:
[Query1].[Status]
Count with formula: count([Query1].[ID])
That will give you the result you're after.
Here's a link to doco on how to nest queries:
http://pic.dhe.ibm.com/infocenter/cx/v10r1m0/topic/com.ibm.swg.ba.cognos.ug_cr_rptstd.10.1.0.doc/c_cr_rptstd_wrkdat_working_with_queries_rel.html?path=3_3_10_6#cr_rptstd_wrkdat_working_with_queries_rel

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