Ya, it is **a duplicate** of [this](https://stackoverflow.com/questions/7781088/does-sql-server-creates-non-clustered-index-on-all-columns-of-a-table-by-default). But I just needs a clarification on [this article](http://blog.sqlauthority.com/2013/02/10/sql-server-primary-key-and-nonclustered-index-in-simple-words/) by **Pinal Dave**, which says the following:

> 
> Scenario 4: Primary Key defaults to Clustered Index with other index
>  defaults to Non-clustered index
> 
> 
> In this case we will create two indexes on the both the tables but we
>  will not specify the type of the index on the columns. When we check
>  the results we will notice that Primary Key is automatically defaulted
>  to Clustered Index and another column as a Non-clustered index.
> 
> 
> 
> ```
> -- Case 4 Primary Key and Defaults
> USE TempDB
> GO
> -- Create table
> CREATE TABLE TestTable
> (ID INT NOT NULL PRIMARY KEY,
> Col1 INT NOT NULL UNIQUE)
> GO
> -- Check Indexes
> SELECT OBJECT_NAME(OBJECT_ID) TableObject,
> [name] IndexName,
> [Type_Desc]
> FROM sys.indexes
> WHERE OBJECT_NAME(OBJECT_ID) = 'TestTable'
> GO
> -- Clean up
> DROP TABLE TestTable
> GO
> 
> ```
> 
>