Is there a way to make a TSQL variable constant?

Is there a way to make a TSQL variable constant?

From stackoverflow TheImirOfGroofunkistan

• There are no such thing as "creating a constant" in database literature. Constants exist as they are and often called values. One can declare a variable and assign a value (constant) to it. From a scholastic view:

  DECLARE @two INT
  SET @two = 2
  

  Here @two is a variable and 2 is a value/constant.

  From Greg Hurlman

• No but you can create a function and hardcode it in there and use that

  Here is an example

  create function fnConstant()
  returns int
  as
  begin
  return 2
  end
  go
  
  select dbo.fnConstant()
  

  From SQLMenace

• No, but good old naming conventions should be used.

  declare @MY_VALUE as int
  

  From jms

• Okay, lets see

  Constants are immutable values which are known at compile time and do not change for the life of the program

  that means you can never have a constant in SQL Server

  declare @myvalue as int
  set @myvalue = 5
  set @myvalue = 10--oops we just changed it
  

  the value just changed

  From SQLMenace

• @ Nick: those are mutable (by calling SET later on), not constant.

  There is no built-in support for constants in T-SQL. You could use SQLMenace's approach to simulate it (though you can never be sure whether someone else has overwritten the function to return something else…), or possibly write a table containing constants, as suggested over here. Perhaps write a trigger that rolls back any changes to the ConstantValue column?

  From Sören Kuklau