Counting the instances of customers
Say that I have a table with one column named CustomerId.
The example of the instance of this table is :
    
    CustomerId
    14
    12
    11
    204
    14
    204

I want to write a query that counts the number of occurences of customer IDs.
At the end, I would like to have a result like this :

    CustomerId      NumberOfOccurences
    14              2
    12              1
    11              1
    204             2
    14              1

I cannot think of a way to do this. 

Counting the instances of customers
===

Say that I have a table with one column named CustomerId.
The example of the instance of this table is :
    
    CustomerId
    14
    12
    11
    204
    14
    204

I want to write a query that counts the number of occurences of customer IDs.
At the end, I would like to have a result like this :

    CustomerId      NumberOfOccurences
    14              2
    12              1
    11              1
    204             2
    14              1

I cannot think of a way to do this. 
