Thank you GilaMonster. Super explanation.

Naveen

Thank you GilaMonster. I completely understood it now.

I appreciate your help

Naveen

I agree with GilaMonster.

Still not getting the difference between those two roles. If both do the same job, why two then?

Sorry if I'm giving trouble to anyone. I appreciate your...

db_datareader -> grants select permissions and doesn't allow you to update anything in the tables (means denying insert, update and delete permissions)

db_denydatawriter -> also doesn't allow you to update anything...