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 added HOLDLOCK which wasn't present originally. Please disregard the version without this hint.

As far as I'm concerned, this should be enough:

INSERT INTO TheTable 
SELECT 
    @primaryKey, 
    @value1, 
    @value2 
WHERE 
    NOT EXISTS 
    (SELECT 0
     FROM TheTable WITH (UPDLOCK, HOLDLOCK)
     WHERE PrimaryKey = @primaryKey) 

Also, if you actually want to update a row if it exists and insert if it doesn't, you might find this question useful.