My table has two columns, declaration_no and invoice_no. I'd like to select declaration_no when the invoice_no...
By submitting your email address, you agree to receive emails regarding relevant topic offers from TechTarget and its partners. You can withdraw your consent at any time. Contact TechTarget at 275 Grove Street, Newton, MA.
on the first version of the declaration_no is not the same as on the last version of declaration_no. I should add that the declaration_no can have values like 001 for the first version, and next versions can have values 001_1, 001_2, and so on.
The design of your declaration_no is very poor. Really, the version number should be a separate column. You will find that the following query will not be very efficient because it needs to perform string functions on the declaration_no column.
select Dmin.declaration_no as min_version , Dmin.invoice_no as min_invoice , cast(substring(Dmax.declaration_no from 5 for char_length(Dmax.declaration_no)-4) as integer) as max_version , Dmax.invoice_no as max_invoice from declarations as Dmin inner join declarations as Dmax on substring(Dmax.declaration_no from 1 for 3) = Dmin.declaration_no and cast(substring(Dmax.declaration_no from 5 for char_length(Dmax.declaration_no)-4) as integer) = ( select max( cast(substring(declaration_no from 5 for char_length(Dmax.declaration_no)-4) as integer) ) from declarations where substring(declaration_no from 1 for 3) = Dmin.declaration_no ) where Dmin.invoice_no <> Dmax.invoice_no
I will leave it as an exercise for you to write the query when the version number is a separate column. It's significantly easier and more efficient.
Related Q&A from Rudy Limeback
Read SQL expert Rudy Limeback's advice for counting combinations in a table with SQL's GROUP BY clausecontinue reading
Read an example of an SQL case expression from our SQL expert Rudy Limeback.continue reading
Read about the Mimer Validator, a tool used to verify your SQL code, in this tip from SQL expert Rudy Limeback.continue reading
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.