Tags » Primary Key

Primary vs Unique Candidate vs Composite Keys

Primary Key Unique Key  Can be only one in a table Can be more than one unique key in one table. It never allows null values Unique key can have null values Primary Key is unique key identifier and can not be null and must be unique. 108 more words

Interview Questions

Primary Key With Non Clustered Index

As a default, SQL Server creates a Primary Key column with a Clustered Index. However, this doesn’t have to be the case. 395 more words


Can't perfrorm Create, Update or Delete operations on Table(..) because it has no primary key

I stumbled upon this logical error after having published a new table in the EPiServer DXC environment and had it deployed to preparation and production. As you may know, you cannot publish changes to the prep and prod databases directly in DXC, due to which I was stranded with having non-functional code just after Friday’s last update window (DXC does not handle update / publish requests on the weekend.) 139 more words


Creating a sample database in Microsoft Access 2007

We talked about what is database and why do people use it ? at this post. Now, we will create a sample database by using… 822 more words

Lecture Notes

Finding primary key candidates

Probably one of the most common challenges I see when I do ETL and business intelligence work is analyzing a table (or a file) for possible… 1,558 more words


UUID vs Auto Increment

What is the best method to create a key in today’s advanced Javascript node.js style applications? Do you rely on the old tried and true method to use auto-increment on the database primary key? 220 more words


Primary Key.

Q153. Define Primary Key.

Ans. Primary Key is set of one or more attributes that can uniquely identify tuples within a relation.