Insert a different value in underlying table when a view is updated - sql

Question

Consider the following example where I have a table and corresponding view:
Table | View
T_EmailAddress | V_EmailAddress
----------------+----------------
ID INT | ID
Status VARCHAR | Status
Valid INT |
Column1 VARCHAR | Column1
ColumnN VARCHAR | ColumnN
I have a program that issues the following queries:
UPDATE V_EmailAddress SET Status = 'valid' WHERE ID = 1;
UPDATE V_EmailAddress SET Status = 'invalid' WHERE ID = 2;
Is it possible to update the underlying table so that the Status valid and invalid is stored as 1 and 0 inside Valid column of the underlying table.
Note that I cannot change the table or the query. However I can add "normal" columns to the table.

Answer 1

You could use an instead of update trigger on the view.
When ever an update statement on the view will be completed, the trigger will fire. Note that instead of trigger means that the update will be blocked, and you will have to write the update statement to the underling table yourself.
Something along these lines should do the trick:
CREATE TRIGGER V_EmailAddress_IO_Update ON V_EmailAddress
INSTEAD OF UPDATE
AS
BEGIN
UPDATE t
SET Column1 = i.Column1,
ColumnN = i.ColumnN,
Valid = CASE WHEN i.[Status] = 'valid' THEN 1 ELSE 0 END
FROM inserted i
INNER JOIN T_EmailAddress t ON i.ID = t.ID
END
Note that you must include all the columns that can be updated in the view in your update statement, otherwise they will not be updated.

Answer 2

You can add an UPDATE TRIGGER:
CREATE TRIGGER T_Valid ON T_EmailAddress
INSTEAD OF UPDATE
AS
BEGIN
UPDATE t
SET ID = i.ID
,Valid = CASE WHEN i.Status = 'Valid' THEN 1 ELSE 0 END
,Status = i.Status
,Column1 = i.Column1
,ColumnN = i.ColumnN
FROM T_EmailAddress t
INNER JOIN ON INSERTED i
ON t.ID = i.ID
END
GO
Alternatively, you may want to replace the Valid column with a computed column:
ALTER TABLE T_EmailAddress
DROP COLUMN Valid
ALTER TABLE T_EmailAddress
ADD Valid AS (CASE WHEN Status = 'Valid' THEN 1 ELSE 0 END) PERSISTED