SQL Trigger on Insert to call a Function and Manipulate Values - sql

Question

I am having a problem knowing set up a trigger on insert to call a function and passing an identifier SiteID to that function which then operates on variables from another table.
I have the table, where values are inserted:
CREATE TABLE [dbo].[Tests] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[SiteID] NVARCHAR (128) NOT NULL,
[Date] NVARCHAR (MAX) NULL,
[Time] NVARCHAR (MAX) NULL,
[Tub] NVARCHAR (MAX) NULL,
[FCl] FLOAT (53) NOT NULL
PRIMARY KEY CLUSTERED ([Id] ASC)
);
Every time a value is inserted in to the Tests table I would like a function to be called which uses the table Review to perform a simple calculation (see the trigger down the post below):
CREATE TABLE [dbo].[Review] (
[SiteID] NVARCHAR (128) NOT NULL,
[TubNum] INT NOT NULL,
[Supplied] INT NULL,
[Performed] INT NULL,
[Remaining] INT NULL
PRIMARY KEY CLUSTERED ([SiteID] ASC)
);
This is my sqlfiddle so far, however, I am unable to save it with the functions I am working on, which are here:
The trigger - not sure how to pass the SiteID for the insert or call the function:
CREATE TRIGGER [dbo].[TRIG_MyTable]
ON [dbo].[Tests]
AFTER INSERT
AS
CALL CalcRemaining() //how to pass it SiteID?
and the the function itself:
CREATE FUNCTION [dbo].[CalcRemaining](#ID NVARCHAR (128))
RETURNS NULL
AS
BEGIN
SELECT (Supplied, Performed FROM Review WHERE SiteID = ID);
Performed = Performed + 1;
INSERT INTO Review (Performed, Remaining) VALUES (Performed, (Supplied-Performed))
RETURN;
END
The idea is that the SiteID from the inserted line is passed to the function when called, the function then selects the values Supplied and Performed for that matching SiteID from the Review table. The Performed value is incremented by 1 and that new value along with the retrieved Supplied value are subtracted and written to the Remaining field in the Review table.

Answer 1

If the assumptions I've asked about in the comments are valid (that Remaining and Performed can always be calculated), here's how I'd implement your database structure, with no trigger nor function:
Base tables:
CREATE TABLE dbo.Tests (
[Id] INT IDENTITY (1, 1) NOT NULL,
[SiteID] NVARCHAR (128) NOT NULL,
[Date] NVARCHAR (MAX) NULL,
[Time] NVARCHAR (MAX) NULL,
[Tub] NVARCHAR (MAX) NULL,
[FCl] FLOAT (53) NOT NULL
PRIMARY KEY CLUSTERED ([Id] ASC)
);
GO
CREATE TABLE dbo._Review (
[SiteID] NVARCHAR (128) NOT NULL,
[TubNum] INT NOT NULL,
[Supplied] INT NULL,
PRIMARY KEY CLUSTERED ([SiteID] ASC)
);
Then a view that calculates Performed:
CREATE VIEW dbo._Tests_Count
WITH SCHEMABINDING
AS
SELECT
SiteID,
COUNT_BIG(*) as Performed
FROM
dbo.Tests t
GROUP BY SiteID
GO
CREATE UNIQUE CLUSTERED INDEX IX_Tests_Count ON dbo._Tests_Count (SiteID)
And finally a view that re-creates the original Review table:
CREATE VIEW dbo.Review
WITH SCHEMABINDING
AS
SELECT
r.SiteID,
r.TubNum,
r.Supplied,
COALESCE(tc.Performed,0) as Performed,
r.Supplied - COALESCE(tc.Performed,0) as Remaining
FROM
dbo._Review r
left join
dbo._Tests_Count tc WITH (NOEXPAND)
on
r.SiteID = tc.SiteID
GO
If needed, at this point a trigger could be created on this Review view to allow any INSERTs, DELETEs and UPDATEs to be performed against it rather than _Review, if you cannot change some calling code.

Answer 2

You have to be completely sure you're manipulating ONLY one row at a time!
CREATE TRIGGER [dbo].[TRIG_MyTable]
ON [dbo].[Tests]
AFTER INSERT
AS
DECLARE #SiteID NVARCHAR (128)
SELECT #SiteID = ID FROM inserted
CALL CalcRemaining(#SiteID)