Using Instead-Of SQL triggers to insert or update a view - sql-server

Question

I want to write a trigger to the view, VW_BANKBRANCH:
If the inserted row contains a bankcode that exists in the table, then update the
bName column of bank table with the inserted data
If not, insert rows to bank table to reflect the new information.
But my trigger is not working..
My tables
CREATE TABLE bank(
code VARCHAR(30) PRIMARY KEY,
bName VARCHAR(50)
);
CREATE TABLE branch(
brNum INT PRIMARY KEY,
brName VARCHAR(50),
braddress VARCHAR(50),
bcode VARCHAR(30) REFERENCES bank(code)
);
CREATE VIEW VW_BANKBRANCH
AS
SELECT code,bname,brnum,brName
FROM bank ,branch
WHERE code=bcode
My trigger
CREATE TRIGGER tr_VW_BANKBRANCH_INSERT ON VW_BANKBRANCH
INSTEAD OF INSERT
AS
BEGIN
DECLARE #insertedBankCode INT
#insertedbname varchar
#insertedbrnum int
#insertedbrName varchar
SELECT #insertedBankCode = code
FROM INSERTED
IF(#insertedBankCode=code)
SET code=#insertedBankCode
bname=#insertedbname
brnum=#insertedbrnum
brName=#insertedbrName
ELSE
insert(code,bname,brnum,brName)
END

Answer 1

I've adapted the instead of trigger on the view below - I'm assuming you want to upsert both bank and branch accordingly (although note that the branch address is not currently in the view).
That said, I would be careful of (ab)using an instead of trigger on an INSERT to do upserts - this might not be entirely intuitive to the reader.
Also, remember that the INSERTED pseudo table could contain a SET of rows, so needs to be adjusted to set based approach accordingly.
CREATE TRIGGER tr_VW_BANKBRANCH_INSERT ON VW_BANKBRANCH
INSTEAD OF INSERT
AS
BEGIN
SET NOCOUNT ON;
UPDATE b
SET bname = i.bname
FROM bank b
INNER JOIN inserted i
ON i.code = b.code;
UPDATE br
SET
br.brName = i.brName,
br.braddress = NULL -- TODO add this to the view
FROM branch br
INNER JOIN inserted i
ON br.bcode = i.code
AND br.brNum = i.brNum;
INSERT INTO bank(code, bname)
SELECT code, bname
FROM inserted i
WHERE NOT EXISTS
(SELECT 1 FROM bank b WHERE b.code = i.Code);
INSERT INTO Branch(brNum, brName, braddress, bcode)
SELECT brNum, brName, NULL, code
FROM inserted i
WHERE NOT EXISTS
(SELECT 1
FROM branch br
WHERE br.bcode = i.Code AND br.brNum = i.brNum);
END;
GO
SqlFiddle here - I've also adjusted the view to use a JOIN, rather than the old style of WHERE joins.
If you have SqlServer 2008 or later, you could also use MERGE instead of separate inserts and updates.