Issue: I want to add "N/A" into my @SQL SELECT

Query: Can I add 'know' values or does I need to declare them and add as per the tableName?

Test: I have tried:

' + 'N/A' + '
and
' + "N/A" + '

Notes: If I remove the N/A line of code it works.

Error: Invalid column name 'N/A'.

Code:

```
USE [DB]
GO
/****** Object:  StoredProcedure [dbo].[spExcelIntoTable]    Script Date: 01/10/2015 13:27:05 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

ALTER PROCEDURE [dbo].[spExcelIntoTable]
(
    @tableName          NVARCHAR(256)     
)
AS
BEGIN

DECLARE @sql NVARCHAR(MAX)

SET @sql = 'SELECT a.ID AS ID,  
a.UPRN,p.BuildingNo,
p.Street,p.Postcode ,
a.ItemRef,a.SurveyDate ,
a.OverallRiskCategory ,
a.SurveyorsComments 

INTO  TEMP_' + @tableName + '

FROM TblAsbestos 

AS a JOIN TblProperty 
As p on a.UPRN = p.UPRN
WHERE a.OverallRiskCategory <> "N/A"
ORDER BY a.OverallRiskCategory'

EXEC (@sql)

END
GO

```