Can a TABLE have primary key without Clustered Index? - Yes | Can a TABLE have Clustered Index without primary key? - Yes

 A primary key is a unique index that is clustered by default. By default means that when you create a primary key, if the table is not clustered yet, the primary key will be created as a clustered unique index. Unless you explicitly specify the nonclustered option.

A clustered index stores all columns at the leaf level. That means a clustered index contains all data in the table. A table without a clustered index is called a heap.

SQL Server Function

 STUFF :

The STUFF() function deletes a part of a string and then inserts another part into the string, starting at a specified position.

Note: Also look at the REPLACE() function.

Syntax:

STUFF(string, start, length, new_string)

Example: 

SELECT STUFF('SQL Tutorial!', 13, 1, ' is fun!');

CharIndex()

The CHARINDEX() function searches for a substring in a string, and returns the position.

If the substring is not found, this function returns 0.

Note: This function performs a case-insensitive search.

Syntax:

CHARINDEX(substring, string, start).

Example:

SELECT CHARINDEX('OM', 'Customer') AS MatchPosition