Write a trigger in sql server

//Write a trigger in sql server
-- =============================================
CREATE TRIGGER [dbo].[trigUpdateDissection_Cat_Vendor]
ON [dbo].[tblProductDissection]
AFTER INSERT,DELETE
AS
BEGIN
DECLARE
@VendorId bigint,
@DissectionId bigint,
@CategoryId bigint,
@ProductId bigint

IF (SELECT Count(*) FROM INSERTED) > 0
BEGIN
SELECT
@ProductId=tblProductDissection.ProductId,
@DissectionId=tblProductDissection.DissectionId

FROM INSERTED tblProductDissection

insert into dbo.tblDissection_Cat_Vendor
(
VendorId,
DissectionId,
CategoryId
)

SELECT VendorId ,@DissectionId,CategoryId from tblProduct where tblProduct.productId=@ProductId
END


--End inserted

IF (SELECT Count(*) FROM DELETED) > 0
BEGIN
SELECT
@ProductId=tblProductDissection.ProductId,
@DissectionId=tblProductDissection.DissectionId

FROM DELETED tblProductDissection

SELECT @VendorId=VendorId from tblProduct where tblProduct.productId=@ProductId
SELECT @CategoryId=CategoryId from tblProduct where tblProduct.productId=@ProductId

DELETE from dbo.tblDissection_Cat_Vendor
WHERE DissectionId=@DissectionId and
CategoryId=@CategoryId and VendorId=@VendorId
END

END