This is all going to have to be pseudo as I am on my phone and have no internet access right now as I have just moved but its bugging the crap out of me. This also means I can't do code blocks please bear with me: I'll try.
I have a table with amounts in it, and I have a table with labels. I want to sum the amounts in the first table grouped by the labels. The problem is, if there are no records for a label existing in the table with the amounts then I don't get a record in the result set for that label. I need a record there with nulls for the amount tables field. Here is what some sample data might look like:
Amount_table:
Columns: id, tpa, amt, link_to_label_table
Data:
1, GTL, 2000, 1
2, GTL, 1000, 1
Label_table:
Columns: link_to_amount_table, label_name
Data:
1, Label1
2, Label2
Query:
Select at.tpa, sum(at.amt) as amt, lt.label_name
From Amount_table as at
Left join Label_tabl lt on lt.link_to_amount_table = at.link_to_label_table
Where at.tpa = 'GTL'
Group by lt.label, at.tpa
Now this returns:
GTL, 3000, Label1
I tried selecting from the labels table then left joining the amount table and it still didn't give my desired results which are:
GTL, 3000, Label1
Null, Null, Label2
Is this possible with the sum and group by? The fields being grouped by have to be there otherwise you get an error.
This is in DB2 by the way. Is there any way possible to get this to return the way I need it? I have to get the labels; they are dynamic.
On the face of it, you want to have your labels table as the dominant table and the amounts table as the one that is outer joined.
SELECT a.tpa, sum(a.amt) as amt, l.label_name
FROM Label_table AS l
LEFT JOIN Amount_table AS a
ON l.link_to_amount_table = a.link_to_label_table
GROUP BY l.label, a.tpa
You have a condition Amount_table.tpa = 'GTL'; it is not entirely clear why you have that, but presumably it is significant with more data in the tables. There are (at least) two ways you can incorporate that condition into the query (other than the one you chose - which eliminates the rows where a.tpa is null).
SELECT a.tpa, sum(a.amt) as amt, l.label_name
FROM Label_table AS l
LEFT JOIN Amount_table AS a
ON l.link_to_amount_table = a.link_to_label_table
AND a.tpa = 'GTL'
GROUP BY l.label, a.tpa
Or:
SELECT a.tpa, sum(a.amt) as amt, l.label_name
FROM Label_table AS l
LEFT JOIN (SELECT *
FROM Amount_table
WHERE tpa = 'GTL') AS a
ON l.link_to_amount_table = a.link_to_label_table
GROUP BY l.label, a.tpa
A decent optimizer will produce the same query plan for both, so it probably doesn't matter which you use. There's an argument that suggests the second alternative is cleaner in that the ON clause is primarily for joining conditions, and the filter condition on a.tpa is not a joining condition. There's another argument that says the first alternative avoids a sub-query and is therefore preferable. I'd validate that the query plans are the same and would probably choose the second, but it is a somewhat nebulous decision based on a mild preference.
You were so close on your second try. Change WHERE to AND. This has the effect of applying at.tpa='GTL' to the JOIN instead of applying it to the filter so you don't filter out the NULLs.
Related
I'm in need of some assistance. I have search and not found what I'm looking for. I have an assigment for school that requires me to use SQL. I have a query that pulls some colunms from two tables:
SELECT Course.CourseNo, Course.CrHrs, Sections.Yr, Sections.Term, Sections.Location
FROM Course
INNER JOIN Sections ON Course.CourseNo = Sections.CourseNo
WHERE Sections.Term="spring";
I need to add a Totals row at the bottom to count the CourseNo and Sum the CrHrs. It has to be done through SQL query design as I need to paste the code. I know it can be done with the datasheet view but she will not accept that. Any advice?
To accomplish this, you can union your query together with an aggregation query. Its not clear from your question which columns you are trying to get "Totals" from, but here's an example of what I mean using your query and getting counts of each (kind of useless example - but you should be able to apply to what you are doing):
SELECT
[Course].[CourseNo]
, [Course].[CrHrs]
, [Sections].[Yr]
, [Sections].[Term]
, [Sections].[Location]
FROM
[Course]
INNER JOIN [Sections] ON [Course].[CourseNo] = [Sections].[CourseNo]
WHERE [Sections].[Term] = [spring]
UNION ALL
SELECT
"TOTALS"
, SUM([Course].[CrHrs])
, count([Sections].[Yr])
, Count([Sections].[Term])
, Count([Sections].[Location])
FROM
[Course]
INNER JOIN [Sections] ON [Course].[CourseNo] = [Sections].[CourseNo]
WHERE [Sections].[Term] = “spring”
You can prepare your "total" query separately, and then output both query results together with "UNION".
It might look like:
SELECT Course.CourseNo, Course.CrHrs, Sections.Yr, Sections.Term, Sections.Location
FROM Course
INNER JOIN Sections ON Course.CourseNo = Sections.CourseNo
WHERE Sections.Term="spring"
UNION
SELECT "Total", SUM(Course.CrHrs), SUM(Sections.Yr), SUM(Sections.Term), SUM(Sections.Location)
FROM Course
INNER JOIN Sections ON Course.CourseNo = Sections.CourseNo
WHERE Sections.Term="spring";
Whilst you can certainly union the aggregated totals query to the end of your original query, in my opinion this would be really bad practice and would be undesirable for any real-world application.
Consider that the resulting query could no longer be used for any meaningful analysis of the data: if displayed in a datagrid, the user would not be able to sort the data without the totals row being interspersed amongst the rest of the data; the user could no longer use the built-in Totals option to perform their own aggregate operation, and the insertion of a row only identifiable by the term totals could even conflict with other data within the set.
Instead, I would suggest displaying the totals within an entirely separate form control, using a separate query such as the following (based on your own example):
SELECT Count(Course.CourseNo) as Courses, Sum(Course.CrHrs) as Hours
FROM Course INNER JOIN Sections ON Course.CourseNo = Sections.CourseNo
WHERE Sections.Term = "spring";
However, since CrHrs are fields within your Course table and not within your Sections table, the above may yield multiples of the desired result, with the number of hours multiplied by the number of corresponding records in the Sections table.
If this is the case, the following may be more suitable:
SELECT Count(Course.CourseNo) as Courses, Sum(Course.CrHrs) as Hours
FROM
Course INNER JOIN
(SELECT DISTINCT s.CourseNo FROM Sections s WHERE s.Term = "spring") q
ON Course.CourseNo = q.CourseNo
There are 2 tables, there is an expected result, the result is to have the total cost of each engagement calculated, there are multiple tests taken during each engagement, each test ranges in cost (all set values), the expected result must be in terms of EngagementId, EngagementCost
The 2 tables, with there respective fields
- EngagementTest (EngagementId, TestId)
- Test (TestId, TestCost)
How would one go calculating the cost of each engagement.
This is as far as i managed to get
SELECT EngagementId, COUNT(TESTId)
FROM EngagementTest
GROUP BY EngagementId;
Try a SUM of the TestCost column rather than a COUNT. COUNT just tells you the number of rows. SUM adds up the values within the rows and gives you a total. Also your existing query doesn't actually use the table that contains the cost data. You can INNER JOIN the two tables via TestId and then GROUP BY the EngagementId so you get the sum of each engagement.
Something like this:
SELECT
ET.EngagementId,
SUM(T.TestCost)
FROM
EngagementTest ET
INNER JOIN Test T
ON T.TestId = ET.TestId
GROUP BY
ET.EngagementId
It can be achieved using below query.
SELECT i.EngagementId, SUM(TestCost)
FROM EngagementTest i
INNER JOIN Test t
ON e.TestId = t.TestId
GROUP BY i.EngagementId
I'm using Access (I normally use SQL Server) for a little job, and I'm getting "enter parameter value" for Night.NightId in the statement below that has a subquery within a subquery. I expect it would work if I wasn't nesting it two levels deep, but I can't think of a way around it (query ideas welcome).
The scenario is pretty simple, there's a Night table with a one-to-many relationship to a Score table - each night normally has 10 scores. Each score has a bit field IsDouble which is normally true for two of the scores.
I want to list all of the nights, with a number next to each representing how many of the top 2 scores were marked IsDouble (would be 0, 1 or 2).
Here's the SQL, I've tried lots of combinations of adding aliases to the column and the tables, but I've taken them out for simplicity below:
select Night.*
,
( select sum(IIF(IsDouble,1,0)) from
(SELECT top 2 * from Score where NightId=Night.NightId order by Score desc, IsDouble asc, ID)
) as TopTwoMarkedAsDoubles
from Night
This is a bit of speculation. However, some databases have issues with correlation conditions in multiply nested subqueries. MS Access might have this problem.
If so, you can solve this by using aggregation with a where clause that chooses the top two values:
select s.nightid,
sum(IIF(IsDouble, 1, 0)) as TopTwoMarkedAsDoubles
from Score as s
where s.id in (select top 2 s2.id
from score as s2
where s2.nightid = s.nightid
order by s2.score desc, s2.IsDouble asc, s2.id
)
group by s.nightid;
If this works, it is a simply matter to join Night back in to get the additional columns.
Your subquery can only see one level above it. so Night.NightId is totally unknown to it hence why you are being prompted to enter a value. You can use a Group By to get the value you want for each NightId then correlate that back to the original Night table.
Select *
From Night
left join (
Select N.NightId
, sum(IIF(S.IsDouble,1,0)) as [Number of Doubles]
from Night N
inner join Score S
on S.NightId = S.NightId
group by N.NightId) NightsWithScores
on Night.NightId = NightsWithScores.NightId
Because of the IIF(S.IsDouble,1,0) I don't see the point is using top.
Let's say I have a table format that looks exactly like this:
I'd like to write a query that locates the maximum station for a given frame and output case (results are grouped by frame & output case) but also return the ordered P (& eventually V2, V3, T, M2 & M3) that would be associated with the maximum station. The desired query is shown below:
I can't for the life of me figure this out. I've posted a copy of the access database to my google drive: https://drive.google.com/folderview?id=0B9VpkDoFQISJOFcwS2RMSGJ5RVk&usp=sharing
select x.*, t.p
from (select frame, outputcase, max(station) as max_station
from tbl
group by frame, outputcase) x
inner join tbl t
on x.frame = t.frame
and x.outputcase = t.outputcase
and x.max_station = t.station
order by x.frame, x.outputcase;
Just as a note to avoid confusion, w/ that second column, t is the table alias, p is the column name.
The subquery, which I've assigned an alias of x, finds the max(station) for each unique combination of (frame, outputcase). That is what you want, but the problem does not stop there, you also want column p. The reason that couldn't be selected in the same query is because you would have had to group by it, and you don't want the max(station) for each combination of (frame, outputcase, p). You want the max(station) for each combination of (frame, outputcase).
Because we couldn't get column p in that first step, we have to join back to the original table using the value we obtained (which I've assigned an alias, max_station), and the obvious join conditions of frame and outputcase. So we join back to the original table on those 3 things, 2 of which are fields on the actual table, one of which was calculated in the subquery (max_station).
Because we've joined back to the original table, we can then select column p from the original table.
Takes a bit to return the query, but the result below provides the desired result:
SELECT t1.*
FROM [Element Forces - Frames] as t1
WHERE t1.Station In (SELECT TOP 1 t2.Station
FROM [Element Forces - Frames] as t2
WHERE t2.Frame = t1.Frame
ORDER BY t2.Station DESC)
ORDER BY t1.Frame ASC, t1.OutputCase ASC;
I still want to thank everyone who posted answers. I'm sure it's just syntax errors on my part that I was struggling with.
Im writing a query that sums order values broken down by product groups - problem is that when I add joins the aggregated SUM gets greatly inflated - I assume its because its adding in duplicate rows. Im kinda new to SQL, but I think its because I need to construct the query with sub selects or nested joins?
All data returns as expected, and my joins pull out the needed data, but the SUM(inv.item_total) AS Value returned is much higher that it should be - SQL below
SELECT so.Company_id, SUM(inv.item_total) AS Value, co.company_name,
agents.short_desc, stock_type.short_desc AS Type
FROM SORDER as so
JOIN company AS co ON co.company_id = so.company_id
JOIN invoice AS inv ON inv.Sorder_id = so.Sorder_id
JOIN sorder_item AS soitem ON soitem.sorder_id = so.Sorder_id
JOIN STOCK AS stock ON stock.stock_id = soitem.stock_id
JOIN stock_type AS stock_type ON stock_type.stype_id = stock.stype_id
JOIN AGENTS AS AGENTS ON agents.agent_id = co.agent_id
WHERE
co.last_ordered >'01-JAN-2012' and so.Sotype_id='1'
GROUP BY so.Company_id,co.company_name,agents.short_desc, stock_type.short_desc
Any guidence on how I should structure this query to pull out an "un-duplicated" SUM(inv.item_total) AS Value much appreciated.
To get an accurate sum, you want only the joins that are needed. So, this version should work:
SELECT so.Company_id, SUM(inv.item_total) AS Value, co.company_name
FROM SORDER so JOIN
company co
ON co.company_id = so.company_id JOIN
invoice inv
ON inv.Sorder_id = so.Sorder_id
group by so.Company_id, co.company_name
You can then add in one join at a time to see where the multiplication is taking place. I'm guessing it has to do with the agents.
It sounds like the joins are not accurate.
First suspect join
For example, would an agent be per company, or per invoice?
If it is per order, then should the join be something along the lines of
JOIN AGENTS AS AGENTS ON agents.agent_id = inv.agent_id
Second suspect join
Can one order have many items, and many invoices at the same time? That can cause problems as well. Say an order has 3 items and 3 invoices were sent out. According to your joins, the same item will show up 3 times means a total of 9 line items where there should be only 3. You may need to eliminate the invoices table
Possible way to solve this on your own:
I would remove all the grouping and sums, and see if you can filter by one invoice produce an unique set of rows for all the data.
Start with an invoice that has just one item and inspect your result set for accuracy. If that works, then add another invoice that has multiple and check the rows to see if you get your perfect dataset back. If not, then the columns that have repeating values (Company Name, Item Name, Agent Name, etc) are usually a good starting point for checking up on why the duplicates are showing up.