I have a table that has the max months column like the one below:
Category MaxMonths Title
X 3 Beginner-1
X 6 Intermediate-1
X 12 Avance-1
X 999 Master-1
Y 3 Beginner-2
Y 6 Intermediate-2
Y 12 Avance-2
Y 999 Master-2
I also have another table with a number of months column like the one below:
User #months Category
A 1 X
B 5 X
C 6 y
D 12 y
E 15 X
How can I write a case statement that shows based on the #months in the second table, what the user's title is?
For example, it needs to show user A's title is Beginner-1. I am able to join the tables using the category column but have a hard time matching the #months with maxMonths
This query finds the maxMonths applicable for each user/category:
select t2.[User], t2.category, min(t1.maxMonths) as maxMonths
from table1 t1
inner join table2 t2 on t1.category = t2.category
and t1.maxMonths >= t2.months
group by t2.[User], t2.category
You can then easily get the title:
select r1.[User], r2.Title
from
(select t2.[User], t2.category, min(t1.maxMonths) as maxMonths
from table1 t1
inner join table2 t2 on t1.category = t2.category
and t1.maxMonths >= t2.months
group by t2.[User], t2.category) r1
inner join table1 r2 on r2.category = r1.category and r2.maxMonths = r1.maxMonths;
Here's your sample data in temp tables:
CREATE TABLE #title(
category CHAR(1)
,maxMonths INT
,title VARCHAR(25)
)
GO
CREATE TABLE #months(
[user] CHAR(1)
,months INT
,category CHAR(1)
)
GO
INSERT INTO #title VALUES
('X',3 ,'Beginner-1')
,('X',6 ,'Intermediate-1')
,('X',12 ,'Avance-1')
,('X',999,'Master-1')
,('Y',3 ,'Beginner-2')
,('Y',6 ,'Intermediate-2')
,('Y',12 ,'Avance-2')
,('Y',999,'Master-2')
GO
INSERT INTO #months VALUES
('A',1 ,'X')
,('B',5 ,'X')
,('C',6 ,'y')
,('D',12,'y')
,('E',15,'X')
GO
You can use the following query to get what you're looking for.
SELECT
#months.[user]
,#months.months
,#months.category
,#title.title
FROM #title
INNER JOIN #months ON #title.category = #months.category
WHERE #title.maxmonths = (
SELECT
MIN(maxmonths)
FROM #title
WHERE maxmonths >= #months.months
)
Explanation: The nested query will limit the results to just the title with the maxMonths just above the actual months
Notes: I wasn't sure if you wanted a match on the months = maxMonth to go up a level or stay down. I assumed the latter, though you can change that by changing the >= in the nested query to >
Also, you used USER as a column name. You should refrain from using that in production environments, as it is a reserved keyword.
Use the following query
Select
T1.User,
T2.Title
from table1 T1
inner join table2 T2 on t1.category = t2.category
Where t2.MaxMonthes = (
Select
min(MaxMonthes)
from table1 T3
Where T3.maxmonthes >= T2.[#months]
and T2.category = T3.category
)
Related
I'd like to combine Table A and Table B at the link below and end up with Table C. What is the best way to do this in SQL? I've thought about creating a composite key between the tables for LedgerID + Year doing an inner join and then unioning the left and right only data. I'm also curious how to avoid duplicating values across rows like Balance = 50.00 ending up in rows for Tires and Windshield.
Try a full outer join, joining on LedgerID and Year, using coalesce to show Table B's LedgerID/Year when Table A's is NULL:
SELECT
COALESCE(A.LedgerID, B.LedgerID) as LedgerID,
COALESCE(A.Year, B.Year) as Year,
A.Title,
A.Payment,
B.Balance
FROM "Table A" AS A
FULL OUTER JOIN "Table B" AS B ON (A.LedgerID=B.LedgerID AND A.Year=B.Year)
--Please try this Query. Since you have only reference LedgerId and Year, the balance will show 50 for both Tires & Windshield
; with cte_Ledger (LedgerId, [year])
AS
(
Select DISTINCT LedgerId, [year]
From tableA
UNION
Select DISTINCT LedgerId, [year]
From tableB
)
select t.LedgerId
, t.[year]
, t1.Title
, T1.Payments
, t2.Balance
FROM cte_Ledger t
left join tableA t1 on t.LedgerId = t1.LedgerId and t.[year] = t1.[year]
left join tableB t2 on t2.LedgerId = t.LedgerId and t2.[year] = t.[year]
I think so, Above Queries will not help to get expected result.
some misunderstanding is with requirement.
For ledgerid = 22 and Year = 2017, have 2 records in table-A and 1 with Table-B. But in expecting result, Balance 50(Record of table-B) is exists with matched first row of Table-A only. As per above all logic it will be with 2 Records where ledgerid = 22, Year = 2017 and Title with "Tires" & "Windshield".
If required same result as mentioned then need to use recursive CTE or ranking function with order of ID column.
Here is my solution after I loaded the tables, another nested case statement may be need to format out the zero on Ledger 24.
Select
[LedgerID],
[Year],
Case when PayRank = 1 then Title else '' end as Title,
Case when PayRank = 1 then convert(varchar(20),Payments) else '' end as
Payments,
Case when BalRank = 1 then convert(varchar(20),Balance) else '' end as
Balance
from(
SELECT
B.[LedgerID]
,B.[Year]
,Rank()Over(Partition by B.LedgerID,Payments order by
B.LedgerID,B.Year,Title) as PayRank
,isnull([Title],'') as Title
,isnull([Payments],0) as Payments
,Rank()Over(Partition by B.LedgerID,B.Year order by
B.LedgerID,B.Year,Payments) as BalRank
,Balance
FROM [TableB] B
left outer join [TableA] A
on A.LedgerID = B.LedgerID
) Query
order by LedgerID,Year
I have a working sql select, which looks like this
[Edited: Im sorry i did one mistake in the question, i edited alias of Table1 but im trying the answers]
SELECT
m.Column1
,t2.Column2
,COALESCE
(
(
SELECT TOP 1 Vat
FROM LinkedDBServer.DatabaseName.dbo.TableName t3
WHERE
m.MaterialNumber = t3.MaterialNumber COLLATE Czech_CI_AS
and t3.Currency = …
and ...
ORDER BY [Date] DESC
), m.Vat
) as Vat
FROM Table1 m
JOIN Table2 t2 on (m.Column1 = t2.Column1)
It works but the problem is that it takes too long and LinkedServer cut my connection because it takes more than 10 minutes. The purpose of the query is to get newer data from a different database if it exists (i get newest data by top and ordering it by date and precondition is that every data in that database is newer than in mine, thats why im using COALESCE).
But my though is if I was able to rewrite it to JOIN it could be faster. But another problem could be I dont have an primary key (and cant change that).
How can I speed that query up ? (Im using SQL Server 2008 R2)
Thank you
Here i attached Estimated Query Plan: (Its readable in browser ZOOM :) Estimation is for 2 Coalesce columns.
Try rewriting query using outer apply
SELECT
t1.Column1
,t2.Column2
,COALESCE(ou.vat, m.Vat) as Vat
FROM Table1 t1
JOIN Table2 m on (m.Column1 = t1.Column1)
outer apply
(
SELECT TOP 1 Vat
FROM LinkedDBServer.DatabaseName.dbo.TableName t3
WHERE
m.MaterialNumber = t3.MaterialNumber COLLATE Czech_CI_AS
and t3.Currency = …
and ...
ORDER BY [Date] DESC
) ou
Another option:
; WITH vat AS (
SELECT MaterialNumber COLLATE Czech_CI_AS As MaterialNumber
, Vat
, Row_Number() OVER (PARTITION BY MaterialNumber ORDER BY "Date" DESC) As sequence
FROM LinkedDBServer.DatabaseName.dbo.TableName
WHERE Currency = ...
AND ...
)
SELECT t1.Column1
, m.Column2
, Coalesce(vat.Vat, m.Vat) As Vat
FROM Table1 As t1
INNER
JOIN Table2 As m
ON m.Column1 = t1.Column1
LEFT
JOIN vat
ON vat.MaterialNumber = m.MaterialNumber
AND vat.sequence = 1
;
I have a View which has a SQL Script as:
Select
a.iAssetId,
ac.eEventCode,
vm.dtUTCDateTime,
g.iGeofenceId,
g.sGeofenceName,
c.sCategoryName,
c.iCategoryId,
s.sSiteName,
s.iSiteId,
CASE WHEN ac.eEventCode = 6 THEN vm.dtUTCDateTime ELSE NULL END as EnterTime,
CASE WHEN ac.eEventCode = 7 THEN vm.dtUTCDateTime ELSE NULL END as ExitTime,
CASE WHEN
a.iAssetId = Lead(a.iAssetId) OVER (ORDER BY a.iAssetId)
AND g.iGeofenceId = Lead(g.iGeofenceId) OVER (ORDER BY a.iAssetId)
AND ac.eEventCode != Lead(ac.eEventCode) OVER (ORDER BY a.iAssetId)
THEN DATEDIFF(minute, vm.dtUTCDateTime, Lead(vm.dtUTCDateTime) OVER (ORDER BY a.iAssetId)) ELSE NULL END as Test
From AssetCommunicationSummary ac
Inner join VehicleMonitoringLog vm on vm.iVehicleMonitoringId = ac.iVehicleMonitoringId
Inner Join Geofences g on g.iGeofenceId = vm.iGeofenceId
Inner Join Assets a on a.iAssetId = ac.iAssetId
Inner Join Categories c on c.iCategoryId = a.iCategoryId
Inner Join Sites s on s.iSiteId = c.iSiteId
Where ac.eEventCode = 6 OR ac.eEventCode = 7
Group by
a.iAssetId,
ac.eEventCode,
vm.dtUTCDateTime,
g.iGeofenceId,
g.sGeofenceName,
c.sCategoryName,
c.iCategoryId,
s.sSiteName,
s.iSiteId
I have used Lead to calculate the Time differenc in minutes for leading rows based on conditions.
I need to now merge the leading Row and the Current Row based on Condition.
Is there a possible way to do this?
The goal is to get the EnterTime and ExitTime in the Same Row with Time Difference in the Column Next to it.
My result is like this:
If your eventcode is always going to be 6 and 7, then you can just join to that table twice using that clause in the join itself. I think I've got the rest of your schema joined up properly below, but if not, you can adjust it around to fit.
Select
a.iAssetId,
vmEnter.dtUTCDateTime,
g.iGeofenceId,
g.sGeofenceName,
c.sCategoryName,
c.iCategoryId,
s.sSiteName,
s.iSiteId,
vmEnter.dtUTCDateTime as EnterTime,
vmExit.dtUTCDateTime as ExitTime,
DATEDIFF(minute, vmEnter.dtUTCDateTime, vmExit.dtUTCDateTime) as ExitTime,
From Sites s
Inner Join Categories c on s.iSiteId = c.iSiteId
Inner Join Assets a on c.iCategoryId = a.iCategoryId
Inner Join AssetCommunicationSummary acEnter on a.iAssetId = acEnter.iAssetId and acEnter.eEventCode = 6
Inner Join VehicleMonitoringLog vmEnter on vmEnter.iVehicleMonitoringId = acEnter.iVehicleMonitoringId
Inner Join AssetCommunicationSummary acExit on a.iAssetId = acExit.iAssetId and acExit.eEventCode = 7
Inner Join VehicleMonitoringLog vmExit on vmExit.iVehicleMonitoringId = acExit.iVehicleMonitoringId
Inner Join Geofences g on g.iGeofenceId = vmEnter.iGeofenceId
You can use this ddl to test and see the idea of what is going on. It's copy and paste ready, if you want to see a difference in times, make sure you wait before you insert each record.
Create table testing
(
Id int ,
Enter DateTime,
Exitt DateTime,
Eventt int,
GeoCode int
)
insert into testing values (1, GETDATE(),null,6,10)
insert into testing values (1, null,GETDATE(),7,10)
insert into testing values (1, GETDATE(),null,6,11)
insert into testing values (1, null,GETDATE(),7,11)
insert into testing values (2, GETDATE(),null,6,10)
insert into testing values (2, null,GETDATE(),7,10)
create table #temp1
(
Id int, EnterTime datetime, GeoCode int
)
create table #temp2
(
Id int, ExitTime datetime, GeoCode int
)
insert into #temp1
Select Id, MAX(Enter), GeoCode from testing where Eventt = 6 group by Id,GeoCode
insert into #temp2
Select Id, MAX(Exitt),GeoCode from testing where Eventt = 7 group by Id,GeoCode
Select t1.Id, t1.EnterTime,t2.ExitTime, t1.GeoCode, DATEDIFF(ss,t1.EnterTime,t2.ExitTime)
from #temp1 t1
inner join #temp2 t2 on t2.Id = t1.Id
and t1.GeoCode = t2.GeoCode
This is basically pseudo code so your going to need to modify, but everything you need is here.
Im gonna guess that eventcode = 6 means thats the intake time
if so two of your data paris dont make much sense as the exit time is before the intake time,
The Query below only accounts for when amd if eventcode 6 = intake time
and the fact that exit time should be before entertime.
query is based on the output you provided and not the view query.
if doing a select * on your view table gives you that output then replace vw_table with yourviewstablename
There are Nulls in the timedif of sqlfiddle because
there was only one instance of assetid 2
assetid 4 and 6 have exit time that happened before entertimes
SQLFIDDLE
select
v1.iAssetid,
v1.EnterTime,
v2.ExitTime,
datediff(minute, v1.Entertime, v2.Exittime) timedif
from vw_table v1
left join vw_table v2 on
v1.iAssetid= v2.iAssetid
and v1.sCategoryNamea = v2.sCategoryNamea
and v2.eEventcode = 7
and v2.dtUTCDatetime >= v1.dtUTCDatetime
where
v1.eEventcode = 6
You can merge two result sets by adding Row_Number to them and then join on that. Like
SELECT DISTINCT tbl1.col1, tbl2.col2
FROM
(SELECT FirstName AS col1, ROW_NUMBER() OVER (ORDER BY FirstName) Number FROM dbo.UBUser) tbl1
INNER JOIN
(SELECT LastName AS col2, ROW_NUMBER() OVER (ORDER BY LastName) Number FROM dbo.UBUser) tbl2
ON tbl1.Number = tbl2.Number
This way you will be able to have EnterTime and ExitTime in the Same Row with Time Difference in the Column Next to it.
Try this
SELECT iAssetid,
iGeoFenceId,
iGeoFenceName,
sCategoryNamea,
iCategoryid,
sSiteName,
Max(EnterTime) As EnterTime,
Min(ExitTime) As ExitTime,
Datediff(minute, Max(EnterTime), Min(ExitTime)) As Timediff
FROM #vw_Table
GROUP BY iAssetid,
iGeoFenceId,
iGeoFenceName,
sCategoryNamea,
iCategoryid,
sSiteName
Hopefully I'm missing a simple solution to this.
I have two tables. One contains a list of companies. The second contains a list of publishers. The mapping between the two is many to many. What I would like to do is bundle or group all of the companies in table A which have any relationship to a publisher in table B and vise versa.
The final result would look something like this (GROUPID is the key field). Row 1 and 2 are in the same group because they share the same company. Row 3 is in the same group because the publisher Y was already mapped over to company A. Row 4 is in the group because Company B was already mapped to group 1 through Publisher Y.
Said simply, any time there is any kind of shared relationship across Company and Publisher, that pair should be assigned to the same group.
ROW GROUPID Company Publisher
1 1 A Y
2 1 A X
3 1 B Y
4 1 B Z
5 2 C W
6 2 C P
7 2 D W
Fiddle
Update:
My bounty version: Given the table in the fiddle above of simply Company and Publisher pairs, populate the GROUPID field above. Think of it as creating a Family ID that encompasses all related parents/children.
SQL Server 2012
I thought about using recursive CTE, but, as far as I know, it's not possible in SQL Server to use UNION to connect anchor member and a recursive member of recursive CTE (I think it's possible to do in PostgreSQL), so it's not possible to eliminate duplicates.
declare #i int
with cte as (
select
GroupID,
row_number() over(order by Company) as rn
from Table1
)
update cte set GroupID = rn
select #i = ##rowcount
-- while some rows updated
while #i > 0
begin
update T1 set
GroupID = T2.GroupID
from Table1 as T1
inner join (
select T2.Company, min(T2.GroupID) as GroupID
from Table1 as T2
group by T2.Company
) as T2 on T2.Company = T1.Company
where T1.GroupID > T2.GroupID
select #i = ##rowcount
update T1 set
GroupID = T2.GroupID
from Table1 as T1
inner join (
select T2.Publisher, min(T2.GroupID) as GroupID
from Table1 as T2
group by T2.Publisher
) as T2 on T2.Publisher = T1.Publisher
where T1.GroupID > T2.GroupID
-- will be > 0 if any rows updated
select #i = #i + ##rowcount
end
;with cte as (
select
GroupID,
dense_rank() over(order by GroupID) as rn
from Table1
)
update cte set GroupID = rn
sql fiddle demo
I've also tried a breadth first search algorithm. I thought it could be faster (it's better in terms of complexity), so I'll provide a solution here. I've found that it's not faster than SQL approach, though:
declare #Company nvarchar(2), #Publisher nvarchar(2), #GroupID int
declare #Queue table (
Company nvarchar(2), Publisher nvarchar(2), ID int identity(1, 1),
primary key(Company, Publisher)
)
select #GroupID = 0
while 1 = 1
begin
select top 1 #Company = Company, #Publisher = Publisher
from Table1
where GroupID is null
if ##rowcount = 0 break
select #GroupID = #GroupID + 1
insert into #Queue(Company, Publisher)
select #Company, #Publisher
while 1 = 1
begin
select top 1 #Company = Company, #Publisher = Publisher
from #Queue
order by ID asc
if ##rowcount = 0 break
update Table1 set
GroupID = #GroupID
where Company = #Company and Publisher = #Publisher
delete from #Queue where Company = #Company and Publisher = #Publisher
;with cte as (
select Company, Publisher from Table1 where Company = #Company and GroupID is null
union all
select Company, Publisher from Table1 where Publisher = #Publisher and GroupID is null
)
insert into #Queue(Company, Publisher)
select distinct c.Company, c.Publisher
from cte as c
where not exists (select * from #Queue as q where q.Company = c.Company and q.Publisher = c.Publisher)
end
end
sql fiddle demo
I've tested my version and Gordon Linoff's to check how it's perform. It looks like CTE is much worse, I couldn't wait while it's complete on more than 1000 rows.
Here's sql fiddle demo with random data. My results were:
128 rows:
my RBAR solution: 190ms
my SQL solution: 27ms
Gordon Linoff's solution: 958ms
256 rows:
my RBAR solution: 560ms
my SQL solution: 1226ms
Gordon Linoff's solution: 45371ms
It's random data, so results may be not very consistent. I think timing could be changed by indexes, but don't think it could change a whole picture.
old version - using temporary table, just calculating GroupID without touching initial table:
declare #i int
-- creating table to gather all possible GroupID for each row
create table #Temp
(
Company varchar(1), Publisher varchar(1), GroupID varchar(1),
primary key (Company, Publisher, GroupID)
)
-- initializing it with data
insert into #Temp (Company, Publisher, GroupID)
select Company, Publisher, Company
from Table1
select #i = ##rowcount
-- while some rows inserted into #Temp
while #i > 0
begin
-- expand #Temp in both directions
;with cte as (
select
T2.Company, T1.Publisher,
T1.GroupID as GroupID1, T2.GroupID as GroupID2
from #Temp as T1
inner join #Temp as T2 on T2.Company = T1.Company
union
select
T1.Company, T2.Publisher,
T1.GroupID as GroupID1, T2.GroupID as GroupID2
from #Temp as T1
inner join #Temp as T2 on T2.Publisher = T1.Publisher
), cte2 as (
select
Company, Publisher,
case when GroupID1 < GroupID2 then GroupID1 else GroupID2 end as GroupID
from cte
)
insert into #Temp
select Company, Publisher, GroupID
from cte2
-- don't insert duplicates
except
select Company, Publisher, GroupID
from #Temp
-- will be > 0 if any row inserted
select #i = ##rowcount
end
select
Company, Publisher,
dense_rank() over(order by min(GroupID)) as GroupID
from #Temp
group by Company, Publisher
=> sql fiddle example
Your problem is a graph-walking problem of finding connected subgraphs. It is a little more challenging because your data structure has two types of nodes ("companies" and "pubishers") rather than one type.
You can solve this with a single recursive CTE. The logic is as follows.
First, convert the problem into a graph with only one type of node. I do this by making the nodes companies and the edges linkes between companies, using the publisher information. This is just a join:
select t1.company as node1, t2.company as node2
from table1 t1 join
table1 t2
on t1.publisher = t2.publisher
)
(For efficiency sake, you could also add t1.company <> t2.company but that is not strictly necessary.)
Now, this is a "simple" graph walking problem, where a recursive CTE is used to create all connections between two nodes. The recursive CTE walks through the graph using join. Along the way, it keeps a list of all nodes visited. In SQL Server, this needs to be stored in a string.
The code needs to ensure that it doesn't visit a node twice for a given path, because this can result in infinite recursion (and an error). If the above is called edges, the CTE that generates all pairs of connected nodes looks like:
cte as (
select e.node1, e.node2, cast('|'+e.node1+'|'+e.node2+'|' as varchar(max)) as nodes,
1 as level
from edges e
union all
select c.node1, e.node2, c.nodes+e.node2+'|', 1+c.level
from cte c join
edges e
on c.node2 = e.node1 and
c.nodes not like '|%'+e.node2+'%|'
)
Now, with this list of connected nodes, assign each node the minimum of all the nodes it is connected to, including itself. This serves as an identifier of connected subgraphs. That is, all companies connected to each other via the publishers will have the same minimum.
The final two steps are to enumerate this minimum (as the GroupId) and to join the GroupId back to the original data.
The full (and I might add tested) query looks like:
with edges as (
select t1.company as node1, t2.company as node2
from table1 t1 join
table1 t2
on t1.publisher = t2.publisher
),
cte as (
select e.node1, e.node2,
cast('|'+e.node1+'|'+e.node2+'|' as varchar(max)) as nodes,
1 as level
from edges e
union all
select c.node1, e.node2,
c.nodes+e.node2+'|',
1+c.level
from cte c join
edges e
on c.node2 = e.node1 and
c.nodes not like '|%'+e.node2+'%|'
),
nodes as (
select node1,
(case when min(node2) < node1 then min(node2) else node1 end
) as grp
from cte
group by node1
)
select t.company, t.publisher, grp.GroupId
from table1 t join
(select n.node1, dense_rank() over (order by grp) as GroupId
from nodes n
) grp
on t.company = grp.node1;
Note that this works on finding any connected subgraphs. It does not assume that any particular number of levels.
EDIT:
The question of performance for this is vexing. At a minimum, the above query will run better with an index on Publisher. Better yet is to take #MikaelEriksson's suggestion, and put the edges in a separate table.
Another question is whether you look for equivalency classes among the Companies or the Publishers. I took the approach of using Companies, because I think that has better "explanability" (my inclination to respond was based on numerous comments that this could not be done with CTEs).
I am guessing that you could get reasonable performance from this, although that requires more knowledge of your data and system than provided in the OP. It is quite likely, though, that the best performance will come from a multiple query approach.
Here is my solution SQL Fiddle
The nature of the relationships require looping as I figure.
Here is the SQL:
--drop TABLE Table1
CREATE TABLE Table1
([row] int identity (1,1),GroupID INT NULL,[Company] varchar(2), [Publisher] varchar(2))
;
INSERT INTO Table1
(Company, Publisher)
select
left(newid(), 2), left(newid(), 2)
declare #i int = 1
while #i < 8
begin
;with cte(Company, Publisher) as (
select
left(newid(), 2), left(newid(), 2)
from Table1
)
insert into Table1(Company, Publisher)
select distinct c.Company, c.Publisher
from cte as c
where not exists (select * from Table1 as t where t.Company = c.Company and t.Publisher = c.Publisher)
set #i = #i + 1
end;
CREATE NONCLUSTERED INDEX IX_Temp1 on Table1 (Company)
CREATE NONCLUSTERED INDEX IX_Temp2 on Table1 (Publisher)
declare #counter int=0
declare #row int=0
declare #lastnullcount int=0
declare #currentnullcount int=0
WHILE EXISTS (
SELECT *
FROM Table1
where GroupID is null
)
BEGIN
SET #counter=#counter+1
SET #lastnullcount =0
SELECT TOP 1
#row=[row]
FROM Table1
where GroupID is null
order by [row] asc
SELECT #currentnullcount=count(*) from table1 where groupid is null
WHILE #lastnullcount <> #currentnullcount
BEGIN
SELECT #lastnullcount=count(*)
from table1
where groupid is null
UPDATE Table1
SET GroupID=#counter
WHERE [row]=#row
UPDATE t2
SET t2.GroupID=#counter
FROM Table1 t1
INNER JOIN Table1 t2 on t1.Company=t2.Company
WHERE t1.GroupID=#counter
AND t2.GroupID IS NULL
UPDATE t2
SET t2.GroupID=#counter
FROM Table1 t1
INNER JOIN Table1 t2 on t1.publisher=t2.publisher
WHERE t1.GroupID=#counter
AND t2.GroupID IS NULL
SELECT #currentnullcount=count(*)
from table1
where groupid is null
END
END
SELECT * FROM Table1
Edit:
Added indexes as I would expect on the real table and be more in line with the other data sets Roman is using.
You are trying to find all of the connected components of your graph, which can only be done iteratively. If you know the maximum width of any connected component (i.e. the maximum number of links you will have to take from one company/publisher to another), you could in principle do it something like this:
SELECT
MIN(x2.groupID) AS groupID,
x1.Company,
x1.Publisher
FROM Table1 AS x1
INNER JOIN (
SELECT
MIN(x2.Company) AS groupID,
x1.Company,
x1.Publisher
FROM Table1 AS x1
INNER JOIN Table1 AS x2
ON x1.Publisher = x2.Publisher
GROUP BY
x1.Publisher,
x1.Company
) AS x2
ON x1.Company = x2.Company
GROUP BY
x1.Publisher,
x1.Company;
You have to keep nesting the subquery (alternating joins on Company and Publisher, and with the deepest subquery saying MIN(Company) rather than MIN(groupID)) to the maximum iteration depth.
I don't really recommend this, though; it would be cleaner to do this outside of SQL.
Disclaimer: I don't know anything about SQL Server 2012 (or any other version); it may have some kind of additional scripting ability to let you do this iteration dynamically.
This is a recursive solution, using XML:
with a as ( -- recursive result, containing shorter subsets and duplicates
select cast('<c>' + company + '</c>' as xml) as companies
,cast('<p>' + publisher + '</p>' as xml) as publishers
from Table1
union all
select a.companies.query('for $c in distinct-values((for $i in /c return string($i),
sql:column("t.company")))
order by $c
return <c>{$c}</c>')
,a.publishers.query('for $p in distinct-values((for $i in /p return string($i),
sql:column("t.publisher")))
order by $p
return <p>{$p}</p>')
from a join Table1 t
on ( a.companies.exist('/c[text() = sql:column("t.company")]') = 0
or a.publishers.exist('/p[text() = sql:column("t.publisher")]') = 0)
and ( a.companies.exist('/c[text() = sql:column("t.company")]') = 1
or a.publishers.exist('/p[text() = sql:column("t.publisher")]') = 1)
), b as ( -- remove the shorter versions from earlier steps of the recursion and the duplicates
select distinct -- distinct cannot work on xml types, hence cast to nvarchar
cast(companies as nvarchar) as companies
,cast(publishers as nvarchar) as publishers
,DENSE_RANK() over(order by cast(companies as nvarchar), cast(publishers as nvarchar)) as groupid
from a
where not exists (select 1 from a as s -- s is a proper subset of a
where (cast('<s>' + cast(s.companies as varchar)
+ '</s><a>' + cast(a.companies as varchar) + '</a>' as xml)
).value('if((count(/s/c) > count(/a/c))
and (some $s in /s/c/text() satisfies
(some $a in /a/c/text() satisfies $s = $a))
) then 1 else 0', 'int') = 1
)
and not exists (select 1 from a as s -- s is a proper subset of a
where (cast('<s>' + cast(s.publishers as nvarchar)
+ '</s><a>' + cast(a.publishers as nvarchar) + '</a>' as xml)
).value('if((count(/s/p) > count(/a/p))
and (some $s in /s/p/text() satisfies
(some $a in /a/p/text() satisfies $s = $a))
) then 1 else 0', 'int') = 1
)
), c as ( -- cast back to xml
select cast(companies as xml) as companies
,cast(publishers as xml) as publishers
,groupid
from b
)
select Co.company.value('(./text())[1]', 'varchar') as company
,Pu.publisher.value('(./text())[1]', 'varchar') as publisher
,c.groupid
from c
cross apply companies.nodes('/c') as Co(company)
cross apply publishers.nodes('/p') as Pu(publisher)
where exists(select 1 from Table1 t -- restrict to only the combinations that exist in the source
where t.company = Co.company.value('(./text())[1]', 'varchar')
and t.publisher = Pu.publisher.value('(./text())[1]', 'varchar')
)
The set of companies and the set of publishers are kept in XML fields in the intermediate steps, and there is some casting between xml and nvarchar necessary due to some limitations of SQL Server (like not being able to group or use distinct on XML columns.
Bit late to the challenge, and since SQLFiddle seems to be down ATM I'll have to guess your data-structures. Nevertheless, it seemed like a fun challenge (and it was =) so here's what I made from it :
Setup:
IF OBJECT_ID('t_link') IS NOT NULL DROP TABLE t_link
IF OBJECT_ID('t_company') IS NOT NULL DROP TABLE t_company
IF OBJECT_ID('t_publisher') IS NOT NULL DROP TABLE t_publisher
IF OBJECT_ID('tempdb..#link_A') IS NOT NULL DROP TABLE #link_A
IF OBJECT_ID('tempdb..#link_B') IS NOT NULL DROP TABLE #link_B
GO
CREATE TABLE t_company ( company_id int IDENTITY(1, 1) NOT NULL PRIMARY KEY,
company_name varchar(100) NOT NULL)
GO
CREATE TABLE t_publisher (publisher_id int IDENTITY(1, 1) NOT NULL PRIMARY KEY,
publisher_name varchar(100) NOT NULL)
CREATE TABLE t_link (company_id int NOT NULL FOREIGN KEY (company_id) REFERENCES t_company (company_id),
publisher_id int NOT NULL FOREIGN KEY (publisher_id) REFERENCES t_publisher (publisher_id),
PRIMARY KEY (company_id, publisher_id),
group_id int NULL
)
GO
-- example content
-- ROW GROUPID Company Publisher
--1 1 A Y
--2 1 A X
--3 1 B Y
--4 1 B Z
--5 2 C W
--6 2 C P
--7 2 D W
INSERT t_company (company_name) VALUES ('A'), ('B'), ('C'), ('D')
INSERT t_publisher (publisher_name) VALUES ('X'), ('Y'), ('Z'), ('W'), ('P')
INSERT t_link (company_id, publisher_id)
SELECT company_id, publisher_id
FROM t_company, t_publisher
WHERE (company_name = 'A' AND publisher_name = 'Y')
OR (company_name = 'A' AND publisher_name = 'X')
OR (company_name = 'B' AND publisher_name = 'Y')
OR (company_name = 'B' AND publisher_name = 'Z')
OR (company_name = 'C' AND publisher_name = 'W')
OR (company_name = 'C' AND publisher_name = 'P')
OR (company_name = 'D' AND publisher_name = 'W')
GO
/*
-- volume testing
TRUNCATE TABLE t_link
DELETE t_company
DELETE t_publisher
DECLARE #company_count int = 1000,
#publisher_count int = 450,
#links_count int = 800
INSERT t_company (company_name)
SELECT company_name = Convert(varchar(100), NewID())
FROM master.dbo.fn_int_list(1, #company_count)
UPDATE STATISTICS t_company
INSERT t_publisher (publisher_name)
SELECT publisher_name = Convert(varchar(100), NewID())
FROM master.dbo.fn_int_list(1, #publisher_count)
UPDATE STATISTICS t_publisher
-- Random links between the companies & publishers
DECLARE #count int
SELECT #count = 0
WHILE #count < #links_count
BEGIN
SELECT TOP 30 PERCENT row_id = IDENTITY(int, 1, 1), company_id = company_id + 0
INTO #link_A
FROM t_company
ORDER BY NewID()
SELECT TOP 30 PERCENT row_id = IDENTITY(int, 1, 1), publisher_id = publisher_id + 0
INTO #link_B
FROM t_publisher
ORDER BY NewID()
INSERT TOP (#links_count - #count) t_link (company_id, publisher_id)
SELECT A.company_id,
B.publisher_id
FROM #link_A A
JOIN #link_B B
ON A.row_id = B.row_id
WHERE NOT EXISTS ( SELECT *
FROM t_link old
WHERE old.company_id = A.company_id
AND old.publisher_id = B.publisher_id)
SELECT #count = #count + ##ROWCOUNT
DROP TABLE #link_A
DROP TABLE #link_B
END
*/
Actual grouping:
IF OBJECT_ID('tempdb..#links') IS NOT NULL DROP TABLE #links
GO
-- apply grouping
-- init
SELECT row_id = IDENTITY(int, 1, 1),
company_id,
publisher_id,
group_id = 0
INTO #links
FROM t_link
-- don't see an index that would be actually helpful here right-away, using row_id to avoid HEAP
CREATE CLUSTERED INDEX idx0 ON #links (row_id)
--CREATE INDEX idx1 ON #links (company_id)
--CREATE INDEX idx2 ON #links (publisher_id)
UPDATE #links
SET group_id = row_id
-- start grouping
WHILE ##ROWCOUNT > 0
BEGIN
UPDATE #links
SET group_id = new_group_id
FROM #links upd
CROSS APPLY (SELECT new_group_id = Min(group_id)
FROM #links new
WHERE new.company_id = upd.company_id
OR new.publisher_id = upd.publisher_id
) x
WHERE upd.group_id > new_group_id
-- select * from #links
END
-- remove 'holes'
UPDATE #links
SET group_id = (SELECT COUNT(DISTINCT o.group_id)
FROM #links o
WHERE o.group_id <= upd.group_id)
FROM #links upd
GO
UPDATE t_link
SET group_id = new.group_id
FROM t_link upd
LEFT OUTER JOIN #links new
ON new.company_id = upd.company_id
AND new.publisher_id = upd.publisher_id
GO
SELECT row = ROW_NUMBER() OVER (ORDER BY group_id, company_name, publisher_name),
l.group_id,
c.company_name, -- c.company_id,
p.publisher_name -- , p.publisher_id
from t_link l
JOIN t_company c
ON l.company_id = c.company_id
JOIN t_publisher p
ON p.publisher_id = l.publisher_id
ORDER BY 1
At first sight this approach hasn't been tried yet by anyone else, interesting to see how this can be done in a variety of ways... (preferred not to read them upfront as it would spoil the puzzle =)
Results look as expected (as far as I understand the requirements and the example) and performance isn't too shabby either although there is no real indication on the amount of records this should work on; not sure how it would scale but don't expect too many problems either...
Given the table definition:
create table mytable (
id integer,
mydate datetime,
myvalue integer )
I want to get the following answer by a single SQL query:
id date_actual value_actual date_previous value_previous
where:
date_previous is the maximum of all the dates preceeding date_actual
for each id and values correspond with the two dates
{max(date_previous) < date_actual ?}
How can I achieve that?
Thanks for your hints
This is a variation of the common "greatest N per group" query which comes up every week on StackOverflow.
SELECT m1.id, m1.mydate AS date_actual, m1.myvalue AS value_actual,
m2.mydate AS date_previous, m2.myvalue AS value_previous
FROM mytable m1
LEFT OUTER JOIN mytable m2
ON (m1.id = m2.id AND m1.mydate > m2.mydate)
LEFT OUTER JOIN mytable m3
ON (m1.id = m3.id AND m1.mydate > m3.mydate AND m3.mydate > m2.mydate)
WHERE m3.id IS NULL;
In other words, m2 is all rows with the same id and a lesser mydate, but we want only the one such that there is no row m3 with a date between m1 and m2. Assuming the dates are unique, there will only be one row in m2 where this is true.
Assuming I understood your requirements correctly, here's something you can try.
select a.id,
a.mydate as date_actual,
a.value as value_actual,
b.date as date_previous,
b.value as value_previous
from mytable a, mytable b
where a.id = b.id and
a.mydate > b.mydate and
b.mydate = (select max(mydate) from mytable c where c.id = a.id and c.mydate < a.mydate)
Apologies for the ugly SQL. I am sure there are better ways of doing this.