146 reputation
3
bio website
location
age
visits member for 1 year, 11 months
seen Apr 10 at 16:06

Nov
13
answered Commonly Used Acronyms by Database Administrators
Nov
13
awarded  Supporter
Nov
7
comment a question in tables relations
In this case, each table's record count will be like this: COUNTRY < CITY < STREET (e.g. 100 < 1000 < 100000, respectively). We usually want to retrive some records from STREET table mainly, and want to know what COUNTRY is for each STREET. So, performance issues at CITY or COUNTRY table are less than at STREET table. But really some cases (e.g. CITY table has extremly big /or want to pull up a performance by millisecond), they do denormalization,.. only for specific reason. Denormalization is not recommended in most cases.
Nov
7
comment a question in tables relations
I suggest you that avoid a denormalization as possible as you can (It means do not link between COUNTRY and STREET tables in both cases.) It's natural and right for data modeling. What I said-joining two tables is better than three table in performance perspective- is right, but have a very little difference.
Nov
7
comment a question in tables relations
Thank you, ypercube, also for correcting. I uploaded my images.
Nov
7
awarded  Editor
Nov
7
revised a question in tables relations
deleted 16 characters in body
Nov
7
awarded  Teacher
Nov
7
comment a question in tables relations
I'm also rookie in English. If you find any awkward expressions or mistakes, please feel free to edit. It really helps me. Thank you.
Nov
7
answered a question in tables relations