SQL trigger to avoid duplicates with multiple IDs - sql-server-2008

Question

Good morning,
I found the solution to my problem, but I thought I'd share it anyway as it might be useful for future projects/problems. I have a simple SQL table below which will be the foreign key of my much bigger table of stock prices market data.
CREATE TABLE [StockMarket]
(
[ID] INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
[ReutersRIC] VARCHAR(50),
[BloombergTicker] VARCHAR(50),
[YahooSymbol] VARCHAR(50)
/* other irrelevant columns here*/
)
With that in mind, I am trying to add robustness to the structure as I will be adding from different data sources. For each underlying time series on the financial markets, there are multiple names depending on which data provider you use. I wanted to avoid having multiple lines with different data sources representing the same time series. I needed a trigger which:
1) If the inserted values are not yet in the table, it is simply inserted.
2) if I insert a line for which at least one [ReutersRIC], [BloombergTicker], [YahooSymbol], [ISIN] already exists, I update that specific line instead.
2.1) The update should only happen on Non-Null entrees
My question was how this can be achieved in the best possible way? It took me some time, but I wanted to share the answer below for future reference.

Answer 1

Here is my solution:
CREATE TRIGGER UniqueStockMarketInserts ON [dbo].[StockMarket]
INSTEAD OF INSERT
AS
BEGIN
DECLARE #StockId int
SELECT #StockId = S.ID
FROM [StockMarket] S INNER JOIN [INSERTED] I
ON
S.YahooSymbol = I.YahooSymbol OR
S.ReutersRIC = I.ReutersRIC OR
S.BloombergTicker = I.BloombergTicker OR
S.ISIN = I.ISIN
IF #StockId IS NULL
BEGIN
INSERT INTO [StockMarket] (YahooSymbol,ReutersRIC,BloombergTicker,ISIN)
SELECT I.YahooSymbol, I.ReutersRIC, I.BloombergTicker, I.ISIN
FROM [INSERTED] I
END
ELSE
BEGIN
UPDATE S SET
S.ISIN = ISNULL(S.ISIN,I.ISIN),
S.YahooSymbol = ISNULL(S.YahooSymbol,I.YahooSymbol),
S.ReutersRIC = ISNULL(S.ReutersRIC,I.ReutersRIC),
S.BloombergTicker = ISNULL(S.BloombergTicker,I.BloombergTicker)
FROM INSERTED I, StockMarket S
WHERE S.ID = #StockId
END
END
GO
Here is the test I ran on it with real-life examples (except the ISIN which I made up):
/*-----------TESTING THE TRIGGER--------*/
INSERT INTO StockMarket (ReutersRIC, BloombergTicker) VALUES ('G.TO', 'GG US Equity');
INSERT INTO StockMarket (YahooSymbol, BloombergTicker, ISIN) VALUES ('GOOG', 'GOOG US Equity','US123454321');
INSERT INTO StockMarket (YahooSymbol, ISIN) VALUES ('RDSA','NL111112222')
INSERT INTO StockMarket (YahooSymbol, ReutersRIC) VALUES ('GG', 'G.TO'); /*this should update as per trigger*/
INSERT INTO StockMarket (ReutersRIC, ISIN) Values ('GOOG.OQ','US123454321'); /*this should update as per trigger*/
INSERT INTO StockMarket (YahooSymbol, ReutersRIC) Values ('RDSA', 'RDSa.L'); /*this should update as per trigger*/
And the results:
Hope this can help someone in the future. Happy coding