[Solved] Can some expert please explain what this query is doing? [duplicate]

by


ROW_NUMBER in a subquery combined with a filter on it in the outer query is an idiom to filter out all but the first row in a group. So here

ROW_NUMBER() OVER(PARTITION BY [dbo].[RegistrationHistory].[SerialNumber])

Assigns the row with the lowest SerialNumber 1, the next lowest, 2, etc. Then later

where
   t.seq = 1

removes all but the row with the lowest serial number from the result.

solved Can some expert please explain what this query is doing? [duplicate]