How to write a SQL query to generate a report - sql

Question

I need to generate a report based on the following tables:
CALLS_FOR_PROPOSALS
ID|Name
--+------
1|Call 1
2|Call 2
3|Call 3
PROPOSALS
ID|Call ID|Title
--+-------+----------
1| 1|Proposal 1
2| 2|Proposal 2
3| 2|Proposal 3
PROPOSAL_STATUSES
ID|Proposal ID|Status ID
--+-----------+---------
1| 1| 1
2| 2| 1
3| 3| 1
4| 3| 2
STATUSES
ID|NAME
--+------------
1|Not Reviewed
2|Processing
3|Accepted
4|Rejected
With this sample data, there are 3 Calls for Proposals. There are three Proposals; one for Call 1, and two for Call 2. (Call 3 does not have any proposals.) Each proposal has at least one status assigned to it. When a row is inserted into the PROPOSALS table, a corresponding row is inserted into PROPOSAL_STATUSES, giving the Proposal an initial default status of 1 (Not Reviewed). Each time the status is changed, a new row is inserted into the PROPOSAL_STATUSES table, so that the history of status changes is preserved. I need to generate a report that shows for each Call, the number of Proposals submitted, and the number of Proposals that have had more than one status (i.e. the status has been changed from the default at least once.) For the sample data above, the results would look like this:
Call Name|Proposals Submitted|Proposals Reviewed|
---------+-------------------+------------------+
Call 1 | 1| 0|
Call 2 | 2| 1|
Call 3 | 0| 0|
How would I write the SQL query to generate this report based on the above table structure? Thanks for your help.

Answer 1

something like that should do the trick : Demo
SELECT Name as 'Call name',
submitted as 'Proposals Submitted',
SUM(CASE WHEN maxStatus > 1 THEN 1 ELSE 0 END) as 'Proposals Reviewed'
FROM
(SELECT cfp.Name,
sum(case when ps.Status_ID = 1 then 1 else 0 end) as submitted,
MAX(ps.Status_ID) as maxStatus
FROM CALLS_FOR_PROPOSALS cfp
LEFT JOIN PROPOSALS p on cfp.ID = p.CALL_ID
LEFT JOIN PROPOSAL_STATUSES ps on ps.PROPOSAL_ID = p.ID
GROUP BY cfp.Name) AS s
GROUP BY Name, submitted