My Table looks like something below
Id | Customer_number | Customer_Name | Customer_owner
I want to insert Customer_Number as a sequence specific to Customer_owner
that is 1,2,3,.... for Customer_owner X and 1,2,3,... Customer_owner Y.
To get the Customer_number I can use following SQL
SELECT COUNT(*) FROM Customer where Customer_owner='X'
My question is that are there any performance impact. Specially for a table with 100,000 records. Are there any better alternatives?