Rules in SQL Server 2005

Question

The syntax for rules in SQL Server 2005 is given:

CREATE RULE [ schema_name . ] rule_name 
AS condition_expression

Whenever using rule, for example:

CREATE RULE list_rule
AS 
@list IN ('1389', '0736', '0877');

Why are we using a variable like @list in it? It doesn't correspond to the table name or anything. Is that used for storing the values given in the IN statement or anything else?

I just need an explanation for this. I know that rules are now deprecated but I am using SQL Server 2005.

Answer 1

From MSDN

*condition_expression* includes one variable. The at sign (@) precedes each local variable. The expression refers to the value entered with the UPDATE or INSERT statement. Any name or symbol can be used to represent the value when creating the rule, but the first character must be the at sign (@).

http://msdn.microsoft.com/en-us/library/ms188064.aspx