SQL - INSERT text into field WHERE ___ - sql

Question

I'm looking to add a note to each of my accounts whenever I make contact via a mass email. I'm looking at something like this so far:
INSERT INTO Customer_notes (Note_text)
VALUES ('emailed June 1st')
WHERE Customer_Level = 'Alpha'
This obviously doesn't work, and UPDATE/SET will replace all of my previous notes.

Answer 1

Well, you could do something like this:
INSERT INTO Customer_notes (Note_text)
Note_Text = COALESCE(Note_text + '
', '') + 'emailed June 1st')
WHERE Customer_Level = 'Alpha';
However, it seems like you need more than one note per customer. So perhaps:
INSERT INTO Customer_notes (Customer_Level, Note_text)
VALUES ('Alpha', Note_Text);
This is assuming that Customer_Level is some sort of customer id.

Answer 2

If you mean add that text to whatever currently exists in Note_text for existing rows, then try this..
UPDATE Customer_notes
SET Note_text = ISNULL(Note_text, '') + ' emailed June 1st'
WHERE Customer_Level = 'Alpha'
{edit based on the fifth comment in this answer}
Ok, then instead of VALUES we are SELECTing off of the same table. Try this (Holy Gawd make a backup first) if the idea is to create another row with EVERY row WHERE Customer_Level = 'Alpha' in this table.
INSERT INTO Customer_Notes (CustomerID, note_text)
SELECT CustomerID, 'emailed June 1st'
FROM CustomerNotes
WHERE Customer_Level = 'Alpha'
This does beg the question if Customer_Level is a subset of all customers, and if the idea here is to only insert one row for EACH of these customers, as opposed to ONE row for each customber/existing rows. You'll have to describe this further for us if this is the case.