Blocking in Transaction in sql server

Blocking occurs if a transaction tries to acquire an executive lock on a resource that another transaction has already lock. The blocked transaction remains blocked until the blocking transaction release the lock.

  

Let’s see the example

I have two transactions and want to update records on the table EMP.

    

There are two windows I opened

Now I am going to run transaction A without commit. This is open transaction.

  

Now I am executing the Transaction B

   

It is still executing. It is locked by Transaction A. So Transaction B is blocked by Transaction A.

When Transaction A is completed then only the transaction will be complete. See now I going to commit the Transaction A. let’s see what happen

  

Once I commit the Transaction A then see the result of the Transaction B.