Hi I am trying to create a query that can give me the best performing program among several companies.
I have a table that has several companies and the programs there are a couple companies that have a program that others do not so I know those will be the best performing. I want a query to say for example.
CompanyTwo,Program One,12.85%
CompanyOne,Program Two,12.56%
CompanyTwo,Program Three,1%
..... and so on...
Table looks like this.
CompanyName, ProgramName,PerformancePercentage,ProgramYear
CompanyOne,Program One,10.04%,2015
CompanyOne,Program Two,12.56%,2015
CompanyTwo,Program One,12.85%,2015
CompanyTwo,Program Two,9.5%,2015
CompanyTwo,Program Three,1%,2015
Your query is a bit complicated and requires either 2 queries or a correlated subquery. Below I provided the latter.
SELECT BestPerfByProg.program, Table1.company, BestPerfByProg.BestPerf
FROM Table1
INNER JOIN (SELECT Table1.program, Max(Table1.Performance) AS BestPerf
FROM Table1
WHERE table1.period = 2015
GROUP BY Table1.program
) AS BestPerfByProg ON (Table1.program = BestPerfByProg.program)
AND (Table1.Performance = BestPerfByProg.BestPerf)
ORDER BY BestPerfByProg.program;
If you want to make it in 2 pieces, start with the part that is between () and save it as BestPerfByProg
Related
I am very confused by the cosmosdb documentation on joins. When I think of a join conventionally, I think of 2 tables, with 1 shared id, on which I perform the join. These 2 tables have different schemas, but the result of the join is a combined table with a merge of the columns from both tables. The join for cosmosdb does not seem to me intuitively congruent with that.
I have a collection with heterogenous data. Each document can have a different structure from the next. I want to count the number of documents that have a value that is present in the result set of a subquery. Intuitively, I want to do something like this:
SELECT COUNT(1) as c
FROM CollectionName as outer
where outer.type = "table"
JOIN ((SELECT c.id from c where c.type = "database") as inner) on outer.databaseId == t.id
// count the number of tables that are in deleted databases
It would seem like I would need to do a join on the result of the subquery with the result of the outer query, and then process that resulting table. But I am not understanding right now how to do that:
Select COUNT(1)
from Collection outer
where outer.type = 'table'
JOIN (select c.id from c IN outer.databaseId where c.type = "database" and c.state = "deleted")
I am constantly getting a 400 with the above query. So how am I supposed to think about joins in cosmosdb?
Cosmos is a document database. It stores and operates on json data which can be in hierarchical format. Joins in Cosmos reference tuples within these hierarchies where they can be projected with other data in the document.
There is a really good article that talks through this at pretty deep level but also have lots of examples too, Joins in Cosmos DB.
This takes some getting used to writing queries like this but once you get the hang of it you'll be ok. You can easily practice queries using the Query Playground that has a bunch of sample queries for nutrition dataset with food and ingredients. Or follow along with the families data in the docs. You can create additional items and then write some queries to see how joins work.
Hope that is helpful.
Currently I am developing an Access 2013 based Application for tracking evaluation information of the school students. The database contains only 3 simple tables:
tblSubjects = Contains different subject information
tblStudents = Contains student's personal information
tblMarks = Contains subject wise evaluation marks for each student
and few other queries based on these 3 tables. Now I have a (bit ugly) sql query like following:
SELECT tblStudents.*,
(SELECT COUNT(*) FROM qryPapers WHERE qryPapers.STUDID=tblStudents.STUDID) AS PAPER_COUNT,
(SELECT SUM(MR_TOTAL) FROM qryPapers WHERE qryPapers.STUDID=tblStudents.STUDID) AS ALL_TOTAL,
(SELECT MIN(MR_TOTAL) FROM qryPapers WHERE qryPapers.STUDID=tblStudents.STUDID AND qryPapers.PAPER_TYPE LIKE 'E?') AS MIN_ELEC,
(SELECT COUNT(*) FROM qryPapers WHERE qryPapers.STUDID=tblStudents.STUDID AND qryPapers.PAPER_TYPE LIKE 'A?') AS LANG_PS,
(SELECT COUNT(*) FROM qryPapers WHERE qryPapers.STUDID=tblStudents.STUDID AND qryPapers.PAPER_TYPE LIKE 'E?') AS ELCT_PS,
IIf([PAPER_COUNT]>5,ALL_TOTAL-MIN_ELEC,ALL_TOTAL) AS [GT],
IIf([LANG_PS]=2 And [ELCT_PS]>=3,'PASS','FAIL') AS STATUS
FROM tblStudents;
The Problem is, whenever I try to run a filter on the STATUS field of this query (Like When STATUS='PASS') the entire ACCESS is first STOPES RESPONDING! and then SHUTS DOWN and RESTARTS.
I have no idea what is going on here. I have seen far more complex queries running perfectly well, but not this one. Any help will be appreciated.
I've experienced this a lot in Access. I don't know the cause of the problem but I just export the query to Excel or create a table based on the query to apply filtering.
I have two tables vendors and customers. My problem is that I want to make the search of the name and in result I get the common data from both the tables(if any exist).
Example: If I search the name John and it exits in both the tables so in result I must get the gridviews of both the tables.
Your question is not quite clear for me. Are you looking for a SQL statement?
Try with:
SELECT * FROM Vendors LEFT JOIN Customers ON Vendors.Name = Customers.Name
or
SELECT * FROM Vendors WHERE Vendors.Name IN (SELECT Customers.Name FROM Customers)
I am using QSQlQuery on a sqlite3 database. To fetch a particular item , I was populating the result from 4 different tables. I thought joining the tables would increase the performance/speed and get the result faster. So I joined 2 tables initially but it takes longer time to fetch the data after joining the tables (?)
Any suggestion on how to improve the performance would be really appreciated. Also, I was looking at the http://qt-project.org/doc/qt-4.8/qsqlquery.html and it is mentioned that using setForwardOnly would increase the performance on some databases. Any idea if it would work for SQLite3?
Thanks!
According to this link,
http://sqlite.org/cvstrac/wiki?p=PerformanceTuning
SQLite implements JOIN USING by translating the USING clausing into some extra WHERE clause terms. It does the same with NATURAL JOIN and JOIN ON. So while those constructs might be helpful to the human reader, they don't really make any difference to SQLite's query optimizer.
-I was wrong to join two tables and expect the fetch to be faster. It does not work with SQLite database. Instead using a "where" clause and joining two results directly definitely has some positive impact on the performance.
(example :
select * from A,B where A.id = B.id where A.id = 1; instead of
select * from A left outer join B on A.id = B.id where A.id = 1)
The SQLite translates first statement to second before compiling and you could save on the small amount of CPU time by directly using the second statement
I have recently stumbled upon a problem with selecting relationship details from a 1 table and inserting into another table, i hope someone can help.
I have a table structure as follows:
ID (PK) Name ParentID<br>
1 Myname 0<br>
2 nametwo 1<br>
3 namethree 2
e.g
This is the table i need to select from and get all the relationship data. As there could be unlimited number of sub links (is there a function i can create for this to create the loop ?)
Then once i have all the data i need to insert into another table and the ID's will now have to change as the id's must go in order (e.g. i cannot have id "2" be a sub of 3 for example), i am hoping i can use the same function for selecting to do the inserting.
If you are using SQL Server 2005 or above, you may use recursive queries to get your information. Here is an example:
With tree (id, Name, ParentID, [level])
As (
Select id, Name, ParentID, 1
From [myTable]
Where ParentID = 0
Union All
Select child.id
,child.Name
,child.ParentID
,parent.[level] + 1 As [level]
From [myTable] As [child]
Inner Join [tree] As [parent]
On [child].ParentID = [parent].id)
Select * From [tree];
This query will return the row requested by the first portion (Where ParentID = 0) and all sub-rows recursively. Does this help you?
I'm not sure I understand what you want to have happen with your insert. Can you provide more information in terms of the expected result when you are done?
Good luck!
For the retrieval part, you can take a look at Common Table Expression. This feature can provide recursive operation using SQL.
For the insertion part, you can use the CTE above to regenerate the ID, and insert accordingly.
I hope this URL helps Self-Joins in SQL
This is the problem of finding the transitive closure of a graph in sql. SQL does not support this directly, which leaves you with three common strategies:
use a vendor specific SQL extension
store the Materialized Path from the root to the given node in each row
store the Nested Sets, that is the interval covered by the subtree rooted at a given node when nodes are labeled depth first
The first option is straightforward, and if you don't need database portability is probably the best. The second and third options have the advantage of being plain SQL, but require maintaining some de-normalized state. Updating a table that uses materialized paths is simple, but for fast queries your database must support indexes for prefix queries on string values. Nested sets avoid needing any string indexing features, but can require updating a lot of rows as you insert or remove nodes.
If you're fine with always using MSSQL, I'd use the vendor specific option Adrian mentioned.