Only inserting a row if it's not already there

Question

I had always used something similar to the following to achieve it:

INSERT INTO TheTable
SELECT
    @primaryKey,
    @value1,
    @value2
WHERE
    NOT EXIST         


        

Answer 1

I've done a similar operation in past using a different method. First, I declare a variable to hold the primary key. Then I populate that variable with the output of a select statement which looks for a record with those values. Then I do and IF statement. If primary key is null, then do insert, else, return some error code.

     DECLARE @existing varchar(10)
    SET @existing = (SELECT primaryKey FROM TABLE WHERE param1field = @param1 AND param2field = @param2)

    IF @existing is not null
    BEGIN
    INSERT INTO Table(param1Field, param2Field) VALUES(param1, param2)
    END
    ELSE
    Return 0
END