INSERT ON DUPLICATE KEY UPDATE with last_insert_id()

Question

im trying to create a function

CREATE FUNCTION `func`(param1 INT, param2 INT, param3 TEXT) RETURNS int(11)
BEGIN
INSERT INTO `table1` (`column1`, `column2`, `column3` ) 
VALUES (param1, param2, param3)
ON DUPLICATE KEY 
UPDATE `time_stamp` = UNIX_TIMESTAMP();
RETURN last_insert_id();
END

this would insert into a table a row if it doesn't exist but otherwise update it. Notice that i returned last_insert_id() which would be correct if the function would insert otherwise would be unpredictable if it updates.

I know the alternative to solving this is using separate SELECTS and identify if it exists; if it exists retrieve the id and update using that id; otherwise just do a plain INSERT.

Now my question: Is there any alternative to doing 2 sql statements as opposed to what i'm doing now?

EDIT 1

Addendum:

there is an auto incremented index. All of the values to be inserted are unique

I'd rather not alter the index since it is being referred in another table..

Answer 1

If a table contains an AUTO_INCREMENT column and INSERT ... UPDATE inserts a row, the LAST_INSERT_ID() function returns the AUTO_INCREMENT value. If the statement updates a row instead, LAST_INSERT_ID() is not meaningful. However, you can work around this by using LAST_INSERT_ID(expr). Suppose that id is the AUTO_INCREMENT column. To make LAST_INSERT_ID() meaningful for updates, insert rows as follows:

INSERT INTO table (a, b, c) VALUES (1, 2, 3)
  ON DUPLICATE KEY UPDATE id = LAST_INSERT_ID(id), c = 3;

Found it on this link. I've never tried it though, but it might help you.

EDIT 1

You might want to check out REPLACE:

REPLACE INTO table1 (column1, column2, column3) VALUES (param1, param2, param3);

This should work for tables with correct PRIMARY KEY/UNIQUE INDEX.

In the end, you'll just have to stick with:

IF (VALUES EXISTS ON TABLE ...)
    UPDATE ...
    SELECT Id;
ELSE
    INSERT ...
    RETURN last_insert_id();
END IF