How to find a record change and raise a flag in T-SQL

Ali Shah
Ali Shah used Ask the Experts™
on
Hi Guys,

I have got a master table which contains the unique records, just like below

JobNo	   BookingStatusID
4363267	   2

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I have got a child table as below
JobNo      BookingStatusDescription      WebSupplierStatusID      WebSupplierStatusDescription      RevisionNo      SupplierID
4363267      Amended                                   2                                           Assigned                                             2                 4969
4363267      Confirmed                                   3                                           Rejected                                             1                  5202
4363267      Amended                                   4                                          Accepted                                             4                  4969
4363267      Amended                                   5                                          Error                                                      3                   4969

WIth in my T-SQL I want to figure out that if the supplier ID has been changed then raise some sort of Flag of 0 or 1. I don't want to use inline UDF as the data contains hundred of thousands of rows.

How do i achieve this. Please note i am using SQL Server 2014

regards
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pritaeasSoftware Engineer

Commented:
What do you mean by raising a flag?

You can use a TRIGGER do detect that the record is updated, and specifically check if the supplier column has changed.
Use a SQL trigger that fires on update to that table and you can code it to do something you want when the supplier field value changes.
Ali ShahSQL Developer

Author

Commented:
I mean in my query if it detects that supplier has changed then i add an extra column if say AmmendedSupplier to True or False.

Well i am not allowed to write any triggers as this is live database. I want to achieve by querying and using TSQL?
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Ryan ChongSoftware Team Lead

Commented:
you can try this:
WITH CTE AS (
	SELECT
	rownum = ROW_NUMBER() OVER (ORDER BY p.jobNo),
	p.*
	FROM yourTable p
)
SELECT
CTE.JobNo
FROM CTE
LEFT JOIN CTE nex ON nex.rownum = CTE.rownum + 1
where nex.SupplierID <> CTE.SupplierID
Group By CTE.JobNo
Order By CTE.JobNo

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script above detect the change of SupplierID in your records in a particular JobNo and show the JobNo accordingly.
Ali ShahSQL Developer

Author

Commented:
Hi Ryan,

Thanks a lot for your help. However it is showing those job numbers where the supplierId has not changed. I need those job numbers where SupplierId has been changed

regards
Ryan ChongSoftware Team Lead

Commented:
>>However it is showing those job numbers where the supplierId has not changed. I need those job numbers where SupplierId has been changed
it was tested before post so it should work just fine.

anyway, you can try this as well:
WITH CTE AS (
	SELECT
	rownum = ROW_NUMBER() OVER (ORDER BY p.jobNo),
	p.*
	FROM yourTable p
)
select a.*, case when b.JobNo is null then 0 else 1 end AmmendedSupplier 
from
yourTable a
left join (
	SELECT
	CTE.JobNo
	FROM CTE
	LEFT JOIN CTE nex ON nex.rownum = CTE.rownum + 1
	where nex.SupplierID <> CTE.SupplierID
	Group By CTE.JobNo
) b
on a.JobNo = b.JobNo

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Ali ShahSQL Developer

Author

Commented:
Hi Ryan,

I really appreciate your help. I have got almost 5 millions records and have tested with few records and am afraid it is not showing the correct data. Please find the images of the two test jobnos below Where it is showing as Ammended supplier but in data supplier id is same
JobNos showing that supplier has been changed but its not the case
Ali ShahSQL Developer

Author

Commented:
Sorry just forgot to attach the query confirming directly from the table
Suppliers confirming from the table
Ryan ChongSoftware Team Lead

Commented:
let me try to diagnose the issue... will get back to you tomorrow when I go back to office.
SharathData Engineer

Commented:
check this.
declare @table table (JobNo int, 
                      BookingStatusDescription varchar(100), 
					  WebSupplierStatusID int, 
					  WebSupplierStatusDescription varchar(100), 
					  RevisionNo int, 
					  SupplierID int)
insert @table values (4363267, 'Amended', 2, 'Assigned', 2, 4969),
                     (4363267, 'Confirmed', 3, 'Rejected', 1, 5202),
					 (4363267, 'Amended', 4, 'Accepted', 4, 4969),
					 (4363267, 'Amended', 5, 'Error', 3, 4969)

;with cte as (
select *,lag(SupplierID) over (order by WebSupplierStatusID) prev_SupplierID 
  from @table)
select *,case when SupplierID <> coalesce(prev_SupplierID, SupplierID) then 0 else 1 end Flag
  from cte
/*
JobNo	BookingStatusDescription	WebSupplierStatusID	WebSupplierStatusDescription	RevisionNo	SupplierID	prev_SupplierID	Flag
4363267	Amended	2	Assigned	2	4969	NULL	1
4363267	Confirmed	3	Rejected	1	5202	4969	0
4363267	Amended	4	Accepted	4	4969	5202	0
4363267	Amended	5	Error	3	4969	4969	1
*/

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Software Team Lead
Commented:
@shah36

try this instead:
WITH CTE AS (
	SELECT
	rownum = ROW_NUMBER() OVER (partition by p.jobNo ORDER BY p.jobNo),
	p.*
	FROM BookingRevision p
)
select a.*, case when b.JobNo is null then 0 else 1 end AmmendedSupplier 
from
BookingRevision a
left join (
	select 
	cte.jobNo from CTE
	LEFT JOIN CTE nex ON nex.rownum = CTE.rownum + 1 and cte.jobNo = nex.jobNo
	where nex.SupplierID is not null
	and nex.SupplierID <> cte.SupplierID
	group by cte.jobNo
) b
on a.JobNo = b.JobNo

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Ali ShahSQL Developer

Author

Commented:
@Ryan Chong. Thanks a lot it worked as expected. Thanks again you are a champ.

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