What is better create new table or add columns in existing table

Question

In my database, i have payment table paymentid, amount, duedate, approvalcode, status, transactionid etc.

payment table has already 15 columns.

if i want to store tip, tax, disount against paymentid.

what is better

create new paymentdetails table with one to one relationship

or

add columns in same payment table?

pls help.

payment table has almost more than 50000 records. so what is really good for database.

Answer 1

With such small tables I don't see a reason for not putting the new columns in the existing table.

You would do that if

• you hit some kind of limits (number of columns, total size of table) of the RDBMS
• the data in the columns is huge and only used in few queries

Answer 2

Generally, I work on the premise that attributes of something/entity/object should be stored against the something/entity/object. Typically, I only split out into a new table when there is a one to many relationship - so an attribute that has multiple values (e.g. person and qualifications held)

I would add them to the payment table - although perhaps you have an order table they would more suitably relate to?

You will need to keep in mind whether you will need indexes over these columns though - if you add indexes, you could overburden your table and deteriorate performance but you would probably only add indexes in instances where you used the columns in joins and they don't sound like the sort of thing you would need to join on.