I am trying to join one record in a table to another using a derived table and am having a bit of trouble figuring out the correct query to do so. What I want to do is have a JOIN of a derived table to a query where the derived table uses where statements depending on data from the outer query that is being joined to. So here is the current code that I am working on:
SELECT a.viewerid, a.id, v.id AS entry, a.jobid, v.sourceid, v.cost, a.applicant
FROM a_views a,
JOIN (
SELECT TOP 1 id, sourceid, cost FROM a_views vt
WHERE vt.viewerid = a.viewerid
AND vt.viewed_at <= a.viewed_at
AND vt.referrer NOT LIKE '%' + vt.hostName + '%'
ORDER BY viewed_at DESC
) v
The derived table is a query of the same table that the outer query uses, and viewerid is a FK to itself across the table where id is a unique auto-incrementing PK. I need to get the latest record in the a_views table where the viewer id's match, the datestamp (viewed_at) is less than the outer datestamp and the referrer column doesn't contain the hostName column.
Sounds like you need APPLY:
SELECT a.viewerid, a.id, v.id AS entry, a.jobid, v.sourceid, v.cost, a.applicant
FROM a_views a
CROSS APPLY (
SELECT TOP 1 id, sourceid, cost FROM a_views vt
WHERE vt.viewerid = a.viewerid
AND vt.viewed_at <= a.viewed_at
AND vt.referrer NOT LIKE '%' + vt.hostName + '%'
ORDER BY viewed_at DESC
) v
Since your query has JOIN I've gone for CROSS APPLY, but you may need OUTER APPLY depending on your exact requirements.
Related
I have a query in MSSQL that needs modification but I am unable to get it working properly. The query now is the following:
SELECT Computer.Id AS ComputerId,
Concat(HardDisk.Id, ' ') disks
FROM Computer
LEFT JOIN HardDisk ON Computer.Id = HardDisk.ComputerId
LEFT JOIN DiskOperationLog ON DiskOperationLog.HardDiskId = HardDisk.Id
I need it to also check in the table DiskOperationLog for an EndTime column and if two DiskOperationLog columns with the same HardDisk.Id exists it only needs to select the DiskOperationLog with the newest date. Is this something you can do? I suspect it can be done using the max(DiskOperationLog.EndTime) but I am unable to get it properly included in my selection.
Any help is highly appreciated!
I need it to also check in the table DiskOperationLog for an EndTime column and if two DiskOperationLog columns with the same HardDisk.Id exists it only needs to select the DiskOperationLog with the newest date.
Your query doesn't seem to use DiskOperationLog -- not for filtering (the query uses LEFT JOIN) and not selecting any columns. Let me assume this is an oversight in the question.
In SQL Server, the simplest method to do what you want uses OUTER APPLY:
SELECT c.Id AS ComputerId, Concat(hd.Id, ' ') disks
FROM Computer c LEFT JOIN
HardDisk hd
ON c.Id = hd.ComputerId OUTER APPLY
(SELECT TOP (1) dol.*
FROM DiskOperationLog dol
WHERE dol.HardDiskId = hd.Id
ORDER BY dol.EndTime DESC
) dol;
APPLY implements a lateral join whihc is a lot like a correlated subquery, with the following differences:
The logic is in the FROM clause.
More than one column can be returned.
More than one row can be returned.
You can use a ROW_NUMBER() clause. You would want to partition by HardDisk.Id and order by DiskOperationLog.EndTime descending.
With Qry1 As (
SELECT Computer.Id AS ComputerId,
Concat(HardDisk.Id, ' ') disks,
DiskOperationLog.EndTime,
ROW_NUMBER() OVER(PARTITION BY HardDisk.Id ORDER BY DiskOperationLog.EndTime DESC) As Seq
FROM Computer
LEFT JOIN HardDisk
ON Computer.Id = HardDisk.ComputerId
LEFT JOIN DiskOperationLog
ON DiskOperationLog.HardDiskId = HardDisk.Id
)
SELECT Computer.Id AS ComputerId,
Concat(HardDisk.Id, ' ') disks,
DiskOperationLog.EndTime,
FROM Qry1
WHERE Seq = 1
BTW, if you're trying to get a list of comma-separated disk numbers in column #2, that is definitely not the way to do it.
Scenario: Have a table with four columns. District_Number, District_name, Data_Collection_Week, enrollments. Each week we get data, BUT sometimes we do not.
Task: My supervisor wants me to produce a query that will let us know, which districts did not submit a given week.
What I have tried is below, but I cannot get a NULL value on those that did not submit a week.
SELECT DISTINCT DistrictNumber, DistrictName, DataCollectionWeek
into #test4
FROM EDW_REQUESTS.INSTRUCTION_DELIVERY_ENROLLMENT_2021
order by DistrictNumber, DataCollectionWeek asc
select DISTINCT DataCollectionWeek
into #test5
from EDW_REQUESTS.INSTRUCTION_DELIVERY_ENROLLMENT_2021
order by DataCollectionWeek
select b.DistrictNumber, b.DistrictName, b.DataCollectionWeek
from #test5 a left outer join #test4 b on (a.DataCollectionWeek = b.DataCollectionWeek)
order by b.DistrictNumber, b.DataCollectionWeek asc
One option uses a cross join of two select distinct subqueries to generate all possible combinations of districts and weeks, and then not exists to identify those that are not available in the table:
select d.districtnumber, w.datacollectionweek
from (select distinct districtnumber from edw_requests.instruction_delivery_enrollment_2021) d
cross join (select distinct datacollectionweek from edw_requests.instruction_delivery_enrollment_2021) w
where not exists (
select 1
from edw_requests.instruction_delivery_enrollment_2021 i
where i.districtnumber = d.districtnumber and i.datacollectionweek = w.datacollectionweek
)
This would be simpler (and much more efficient) if you had referential tables to store the districts and weeks: you would then use them directly instead of the select distinct subqueries.
So table A is an overall table of policy_id information, while table b is policy_id's with claims attached. Not all of the id's in A exist in B, but I want to join the two tables and sum(total claims).
The issue is that the sum is way higher than the actual sum within the table itself.
Here is what I've tried so far:
select a.policy_id, coalesce(sum(b.claim_amt), 0)
from database.table1 as a
left join database2.table2 as b on a.policy_id = b.policy_id
where product_code = 'CI'
group by a.policy_id
The id's that don't exist in b show up just fine with a 0 next to them, it's the ones that do exist where the claim_amt's seem like they're being duplicated heavily in the sum.
I suspect your policy_id in table1 are not unique and that leads to the doubled,tripled ,etc. amounts
You could aggregate the sums from table2 in a CTE to get around this.
WITH CTE AS (
SELECT
policy_id
coalesce(sum(claim_amt), 0) as sum_amt
FROM database2.table2
group by policy_id
)
select a.policy_id, b.sum_amt
from database.table1 as a
left join CTE as b on a.policy_id = b.policy_id
where product_code = 'CI'
Can someone help explain to me how when I have 12 rows in table A and 10 in B and I do an inner join , I would get more rows than
in both A and B ?
Same with left and right joins...
This is just a simplified example. Let me share one of my issues with you
I have 2 views ; which was originally SQL on 2 base tables Culture and Trials.
And then when attempting to add another table Culture Steps, one of the team members separated the SQL into 2 views
Since this produces an error when updating(modification cannot be done as it affects multiple base tables), I would like to get
back to changing the SQL such that I no longer use the views but achieve the same results.
One of the views has
SELECT some columns
FROM dbo.Culture RIGHT JOIN
dbo.Trial ON dbo.Culture.cultureID = dbo.Trial.CultureID LEFT OUTER JOIN
dbo.TrialCultureSteps_view_part1 ON dbo.Culture.cultureID = dbo.TrialCultureSteps_view_part1.cultureID
The other TrialCultureSteps_view_part1 view
SELECT DISTINCT dbo.Culture.cultureID,
(SELECT TOP (1) WeekNr
FROM dbo.CultureStep
WHERE (CultureID = dbo.Culture.cultureID)
ORDER BY CultureStepID) AS normalstartweek
FROM dbo.Culture INNER JOIN
dbo.CultureStep AS CultureStep_1 ON dbo.Culture.cultureID = CultureStep_1.CultureID
So how can I combine the joins the achieve the same results using SQL only on tables without the need for views?
Welcome to StackOverflow! This link might be a good place to start in your understanding of JOINs. Essentially, the 'problem' you describe boils down to the fact that one or more of your sources (Trial, Culture, or the TrialCultureSteps view) has more than one record per CultureID - in other words, the same CultureID (#1) shows up on multiple rows.
Based solely on that ID, I'd execute the following three queries. Anything that is returned by them is the 'cause' of your duplications - the culture ID shows up more than once, so you'll have to JOIN on more than just CultureID. If, as I half-suspect, your view is the one that has multiple Culture IDs, you'll need to modify it to only return one record, or change the way that you JOIN to it.
SELECT *
FROM Trial
WHERE CultureID IN
(
SELECT CultureID
FROM Trial
GROUP BY CultureID
HAVING COUNT(*) > 1
)
ORDER BY CultureID
SELECT *
FROM Culture
WHERE CultureID IN
(
SELECT CultureID
FROM Culture
GROUP BY CultureID
HAVING COUNT(*) > 1
)
ORDER BY CultureID
SELECT *
FROM TrialCultureSteps_view_part1
WHERE CultureID IN
(
SELECT CultureID
FROM TrialCultureSteps_view_part1
GROUP BY CultureID
HAVING COUNT(*) > 1
)
ORDER BY CultureID
Let me know if any of these return values!
The comments explain the JOIN issues. As for rewriting, any views could be replaced with CTEs.
One other way to rewrite the query, would be : (Though having sample data and expected result would make this easier to confirm that it's correct)
;with TrialCultureSteps_view_part1 AS
(
Select Row_number() OVER (Partition BY CultureID ORDER BY CultureStepID) RowNumber
, WeekNr
, CultureID
)
SELECT some columns
dbo.trial LEFT OUTER JOIN
dbo.Culture ON dbo.Culture.cultureID = dbo.Trial.CultureID LEFT OUTER JOIN
TrialCultureSteps_view_part1 ON dbo.Culture.cultureID = dbo.TrialCultureSteps_view_part1.cultureID and RowNumber=1
Access code, I'm less familiar with the syntax, but I know that Row_Number() isn't available and I don't believe it has CTE syntax either. So, we'd need to put in some more nested derived tables.
SELECT some columns
dbo.trial LEFT OUTER JOIN
dbo.Culture ON dbo.Culture.cultureID = dbo.Trial.CultureID LEFT OUTER JOIN
( Select cs.CultureID, cs.WeekNr FROM
( SELECT CultureID, MIN(CultureStepID) CultureStepID
FROM dbo.CultureStep
GROUP BY CultureID
) Fcs INNER JOIN
CultureStep cs ON fcs.cultureStepID=cs.CultureStepID
) TrialCultureSteps_view_part1 ON dbo.Culture.cultureID = TrialCultureSteps_view_part1.cultureID
Assumptions here, is that CultureStepID is a PK for CultureStep. No assumption that a step must exist for each Culture entry.
I am trying to filter a single table (master) by the values in multiple other tables (filter1, filter2, filter3 ... filterN) using only joins.
I want the following rules to apply:
(A) If one or more rows exist in a filter table, then include only those rows from the master that match the values in the filter table.
(B) If no rows exist in a filter table, then ignore it and return all the rows from the master table.
(C) This solution should work for N filter tables in combination.
(D) Static SQL using JOIN syntax only, no Dynamic SQL.
I'm really trying to get rid of dynamic SQL wherever possible, and this is one of those places I truly think it's possible, but just can't quite figure it out. Note: I have solved this using Dynamic SQL already, and it was fairly easy, but not particularly efficient or elegant.
What I have tried:
Various INNER JOINS between master and filter tables - works for (A) but fails on (B) because the join removes all records from the master (left) side when the filter (right) side has no rows.
LEFT JOINS - Always returns all records from the master (left) side. This fails (A) when some filter tables have records and some do not.
What I really need:
It seems like what I need is to be able to INNER JOIN on each filter table that has 1 or more rows and LEFT JOIN (or not JOIN at all) on each filter table that is empty.
My question: How would I accomplish this without resorting to Dynamic SQL?
In SQL Server 2005+ you could try this:
WITH
filter1 AS (
SELECT DISTINCT
m.ID,
HasMatched = CASE WHEN f.ID IS NULL THEN 0 ELSE 1 END,
AllHasMatched = MAX(CASE WHEN f.ID IS NULL THEN 0 ELSE 1 END) OVER ()
FROM masterdata m
LEFT JOIN filtertable1 f ON join_condition
),
filter2 AS (
SELECT DISTINCT
m.ID,
HasMatched = CASE WHEN f.ID IS NULL THEN 0 ELSE 1 END,
AllHasMatched = MAX(CASE WHEN f.ID IS NULL THEN 0 ELSE 1 END) OVER ()
FROM masterdata m
LEFT JOIN filtertable2 f ON join_condition
),
…
SELECT m.*
FROM masterdata m
INNER JOIN filter1 f1 ON m.ID = f1.ID AND f1.HasMatched = f1.AllHasMatched
INNER JOIN filter2 f2 ON m.ID = f2.ID AND f2.HasMatched = f2.AllHasMatched
…
My understanding is, filter tables without any matches simply must not affect the resulting set. The output should only consist of those masterdata rows that have matched all the filters where matches have taken place.
SELECT *
FROM master_table mt
WHERE (0 = (select count(*) from filter_table_1)
OR mt.id IN (select id from filter_table_1)
AND (0 = (select count(*) from filter_table_2)
OR mt.id IN (select id from filter_table_2)
AND (0 = (select count(*) from filter_table_3)
OR mt.id IN (select id from filter_table_3)
Be warned that this could be inefficient in practice. Unless you have a specific reason to kill your existing, working, solution, I would keep it.
Do inner join to get results for (A) only and do left join to get results for (B) only (you will have to put something like this in the where clause: filterN.column is null) combine results from inner join and left join with UNION.
Left Outer Join - gives you the MISSING entries in master table ....
SELECT * FROM MASTER M
INNER JOIN APPRENTICE A ON A.PK = M.PK
LEFT OUTER JOIN FOREIGN F ON F.FK = M.PK
If FOREIGN has keys that is not a part of MASTER you will have "null columns" where the slots are missing
I think that is what you looking for ...
Mike
First off, it is impossible to have "N number of Joins" or "N number of filters" without resorting to dynamic SQL. The SQL language was not designed for dynamic determination of the entities against which you are querying.
Second, one way to accomplish what you want (but would be built dynamically) would be something along the lines of:
Select ...
From master
Where Exists (
Select 1
From filter_1
Where filter_1 = master.col1
Union All
Select 1
From ( Select 1 )
Where Not Exists (
Select 1
From filter_1
)
Intersect
Select 1
From filter_2
Where filter_2 = master.col2
Union All
Select 1
From ( Select 1 )
Where Not Exists (
Select 1
From filter_2
)
...
Intersect
Select 1
From filter_N
Where filter_N = master.colN
Union All
Select 1
From ( Select 1 )
Where Not Exists (
Select 1
From filter_N
)
)
I have previously posted a - now deleted - answer based on wrong assumptions on you problems.
But I think you could go for a solution where you split your initial search problem into a matter of constructing the set of ids from the master table, and then select the data joining on that set of ids. Here I naturally assume you have a kind of ID on your master table. The filter tables contains the filter values only. This could then be combined into the statement below, where each SELECT in the eligble subset provides a set of master ids, these are unioned to avoid duplicates and that set of ids are joined to the table with data.
SELECT * FROM tblData INNER JOIN
(
SELECT id FROM tblData td
INNER JOIN fa on fa.a = td.a
UNION
SELECT id FROM tblData td
INNER JOIN fb on fb.b = td.b
UNION
SELECT id FROM tblData td
INNER JOIN fc on fc.c = td.c
) eligible ON eligible.id = tblData.id
The test has been made against the tables and values shown below. These are just an appendix.
CREATE TABLE tblData (id int not null primary key identity(1,1), a varchar(40), b datetime, c int)
CREATE TABLE fa (a varchar(40) not null primary key)
CREATE TABLE fb (b datetime not null primary key)
CREATE TABLE fc (c int not null primary key)
Since you have filter tables, I am assuming that these tables are probably dynamically populated from a front-end. This would mean that you have these tables as #temp_table (or even a materialized table, doesn't matter really) in your script before filtering on the master data table.
Personally, I use the below code bit for filtering dynamically without using dynamic SQL.
SELECT *
FROM [masterdata] [m]
INNER JOIN
[filter_table_1] [f1]
ON
[m].[filter_column_1] = ISNULL(NULLIF([f1].[filter_column_1], ''), [m].[filter_column_1])
As you can see, the code NULLs the JOIN condition if the column value is a blank record in the filter table. However, the gist in this is that you will have to actively populate the column value to blank in case you do not have any filter records on which you want to curtail the total set of the master data. Once you have populated the filter table with a blank, the JOIN condition NULLs in those cases and instead joins on itself with the same column from the master data table. This should work for all the cases you mentioned in your question.
I have found this bit of code to be faster in terms of performance.
Hope this helps. Please let me know in the comments.