MS SQL Server Openquery and Text Query Execution Study - Single Quote

Purpose: We are going to study how to write a query on Openquery/ Text Query by using right amount of single quote.

Case1: My openquery includes where clauses on Text (nvarchar, char, varchar, etc)

 
Select Product_ID
From Openquery (Server_Name, '
Select
Product_ID
From Table_Product_Hierarchy
Where Class = ''Texbook''
') a

Case2: How to execute a query in text format?

 
DECLARE @TSQL NVARCHAR(MAX);

SET @TSQL = 
'Select '+
'Product_ID '+
'From Table_Product_Hierarchy ';

EXECUTE sp_executesql  @TSQL;

') a

Case3: How to execute an openquery in text format?

 

DECLARE @TSQL2 NVARCHAR(MAX);

SET @TSQL2 = 
'Select Product_ID '+
'From Openquery (Server_Name, '+
'''Select '+
'Product_ID '+
'From Table_Product_Hierarchy '+
''') a ';

EXECUTE sp_executesql  @TSQL2;

') a

Case4: How to execute an openquery includes where clauses on text in text format?

 
DECLARE @TSQL3 NVARCHAR(MAX);

SET @TSQL3 = 
'Select Product_ID '+
'From Openquery (Server_Name, '+
'''Select '+
'Product_ID '+
'From Table_Product_Hierarchy '+
' Where Class = ''''Texbook'''' '+
''') a ';

EXECUTE sp_executesql  @TSQL3;