what is key's in DBMS?

Question

Keys why use

Answer 1

In sql , key refers to a column or a field
for RDBMS , most important thing is to have a primary key field bcz it prevents duplicate values & not allows null value
//when more than 1 fields/keys/columns works together to uniquely identify each record then they together known as "composite key"
//hope it helps ☺

Answer 2

keys