MySQL Add record if there's none

Question

I have a table where I store information about users monthly activities. The table is as follows:

+-------------------------------------------+
|user_id   | month | year | value1 | value2 |
+-------------------------------------------+
|1         | 10    | 15   | 45     | 78     |
+-------------------------------------------+

Let's say I have 3 users with ids 1, 2 and 3.

What I'd like to do is : when I submit the request to display records from the table for a given month and year, display the result above + create records with values set at "0" for that given month and year if user doesn't have record. It'd display this :

+-------------------------------------------+
|user_id   | month | year | value1 | value2 |
+-------------------------------------------+
|1         | 10    | 15   | 45     | 78     |
|2         | 10    | 15   | 0      | 0      |
|3         | 10    | 15   | 0      | 0      |
+-------------------------------------------+

I managed to do it hardcoding it per user-id but I haven't been able to automate it to do: for each user that doesn't exist in ACTIVITIES where month=$month and year=$year insert (user_id,month,year,0,0).

This is what I got:

$result = mysqli_query($conn,"
    SELECT
        * FROM ACTIVITIES
    WHERE
        person_id = '2'
        AND month = '$month'
        AND year = '$year'
    ");

    if(mysqli_affected_rows($conn) > 0)
        {

        }
    else
        {
            mysqli_query($conn,"
            INSERT INTO ACTIVITIES
                (person_id, month, year, value1, value2)
            VALUES
                ('2', $mois, $annee, '0', '0')");
        }

Thx for the help. sb

Answer 1

Try using mysqli_num_rows()

if(mysqli_num_rows($result) > 0){

} else {
    //insert here
}