create user

CREATE LOGIN foo WITH PASSWORD = 'xxxx';   
GO 
 
USE [sales_db] 
CREATE USER foo FOR LOGIN foo;   
GO 
 
ALTER ROLE 'db_datareader' ADD MEMBER 'foo';  
 
USE [sales_db] 
GRANT select ON dbo.table_name  TO foo; 
GO 

Drop user

USE [sales_db] 
ALTER AUTHORIZATION ON SCHEMA::[foo] TO [dbo] 
GO  

USE [sales_db] 
ALTER AUTHORIZATION ON ROLE::[foo] TO [dbo] 
GO
 
USE [sales_db] 
DROP USER foo;   
GO

DROP LOGIN foo; 
GO