Commonly asked question in an interview ?
No, but can have more than one unique keys constraints.
No. But you can do it by using composite primary key, which consists of multiple columns, to uniquely identify each row in a table
no
No,You cannot have two primary keys in one table.But primary can contain multiple fields.When you create table,when you mention primary key you can more then one column which you want.like,CREATE TABLE table_name ( col1 Datatype , col2 Datatype,col3 Datatype, col4 Datatype, PRIMARY KEY (col1,col2,col3) )
No. Because Primary key is an identity to the row. There cannot be two identities against a row.