asked on SQL - Previous/Next Records
I have a table with a GUID ID column and Firstname, Surname fields. I want to be able to select a record using the GUID and also select the previous/next record sorted by the Firstname and Surname fields. So for example, i
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In the example above, I want to select record c5875.... (Kevin) and have the previous/next sorted by the 2nd/3rd column and have it display John (prev) and Tracy (next).
Hope that makes sense.
In the example above, I want to select record c5875.... (Kevin) and have the previous/next sorted by the 2nd/3rd column and have it display John (prev) and Tracy (next).
Hope that makes sense.
Microsoft SQL Server
Last Comment
Pawan Kumar
@Olaf Doschke - LEAD() and LAG() were available from SQL Server 2012.
https://msdn.microsoft.com/en-IN/library/hh213125.aspx
SQL Server 2012 introduces new analytical function LEAD() and LAG(). These functions accesses data from a subsequent row (for lead) and previous row (for lag) in the same result set without the use of a self-join .
NEXT Value Sample example - https://msbiskills.com/2012/07/19/t-sql-2/
Previous Value Sample example - https://msbiskills.com/2012/07/19/t-sql-1/
Enjoy !
https://msdn.microsoft.com/en-IN/library/hh213125.aspx
SQL Server 2012 introduces new analytical function LEAD() and LAG(). These functions accesses data from a subsequent row (for lead) and previous row (for lag) in the same result set without the use of a self-join .
NEXT Value Sample example - https://msbiskills.com/2012/07/19/t-sql-2/
Previous Value Sample example - https://msbiskills.com/2012/07/19/t-sql-1/
Enjoy !
To complete Olaf's suggestion.
select *,
lag(FirstName) over (order by FirstName) Prev,
lead(FirstName) over (order by FirstName) Nxt
from your_table
Sorry, yes, wrong promise. It's 2012+ only.
Bye, Olaf.
Bye, Olaf.
ASKER
Thanks for the responses. That is giving me null values for some reason.
I think the requirement need clarifications:
- What's happening if you have two Johns or Tracys?
- And if you want to select Anne (first record) or Tracy (last record)?
ASKER
Thanks for the response Vitor. I'm selecting the record by GUID, but want to include the previous / next records based on the Firstname, Surname values.
Well, LEAD and LAG only give one sclara value (expression), usually one column of the previous or next row, not the full previous/next row. So you get the next and previous lastname in two extra columns, not as separate rows.
You could query the guids you need to query:
Bye, Olaf.
You could query the guids you need to query:
select GUID,
lag(guid) over (order by FirstName, SurName) PrevGUID,
lead(guid) over (order by FirstName, SurName) NxtGUID
from your_table WHERE GUID = '...'
Bye, Olaf.
I understand you're selecting by GUID but you're getting the previous and next records based in the firstname order and not in the GUID.
Like, Tracy's GUID is not the next one after Kevin's (it should by Geoff's by your example).
Like, Tracy's GUID is not the next one after Kevin's (it should by Geoff's by your example).
>> That is giving me null values for some reason.
post some sample data where you are getting NULLs.
post some sample data where you are getting NULLs.
You get NULLS because the main query only fetches one row, you can only get next and previous rows, if the result has more than the one row, that's the problem here.
This is going round in circles, if you first don't know the next and previous neighbors you have to row_number all and then you might also fetch all anyway, and scroll to the one guid.
Bye, Olaf.
This is going round in circles, if you first don't know the next and previous neighbors you have to row_number all and then you might also fetch all anyway, and scroll to the one guid.
Bye, Olaf.
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ASKER
I'll try that and revert.
John, any update of this question?
Hey John, Just wanted to check, have you checked code/post i mentioned.?
Bye, Olaf.