Automatic Table Filter

Hello,

Here is my problem:


I use SQL Server 2005. I have approx. 50 tables in my database and 30 of them have a filed named "CompanyID". Example:
create table A (ID int identity, NAME varchar(100), COMPANYID int)
create table A (ID int identity, REF_ID int, FIELD1 varchar(100), FIELD2 varchar(100), COMPANYID int)

Also there are nearly 200 stored procedures that read data from these tables. Example:
create procedure ABC
as
begin
/*
some checks and expressions here
...
*/
select ...
from A inner join
B on (A.ID = B.REF_ID)
where ...
/* ... */
end;

All my queries in the Stored procedure does not filter the tables by CompanyID, so they process the entire data.

However, now we have a requirement to separate the data for each company. That means that we have to put a filter by CompanyID to each of those 20 tables in each query where the tables appear.

Firstly, I put the CompanyID in the context so now its value is accessible through the context_info() function. Thus I do not need now to pass it as a parameter to the stored procedures.

However, I don't know what is the easiest and fastest way to filter the tables. Example:

I modified the above mentioned procedure in the following way:
create procedure ABC
as
begin
/*
some checks and expressions here
...
*/
-- gets the CompanyID from the context:
DECLARE @CompanyID int;
SELECT @CompanyID = CONVERT(float, CONVERT(varchar(128), context_info()))
select ...
from A inner join
B on (A.ID = B.REF_ID)
where ...
and A.COMPANYID = @CompanyID
and B.COMPANYID = @CompanyID
/* ... */
end;

Now I have the desired filter by CompanyID. However, modifying over 200 stored procedures is rather tedious work and I don't think that this is the best approach. Is there any functionality in SQL Server that can provide the possibility to put an automatic filter to the tables.
For example: when I wrote "SELECT * FROM A", the actual statements to be executed would be "SELECT * FROM A WHERE CompanyID = CONVERT(float, CONVERT(varchar(128), context_info()))".

I was looking for something like "INSTEAD OF SELECT" triggers but I didn't manage to find any answer.

I would very grateful is someone suggests a solution for something like "global table filter" (that will help me make an easy refactoring)?


Thanks in advance.

Best regards,
Beroetz