计算MySQL表中给定值之前的行数

Question

I've searched for quite a while for an answer to this with no luck. Sorry if this is answered somewhere I couldn't find.

I basically have a queue in a MySQL table and I need to tell people what number they are in the queue using PHP.

Right now, I've got this, but all it does is count the number of rows in the table:

$rowquery = "SELECT * FROM restaurant_guests ORDER BY ID UNTIL";
if ($stmt = $mysqli2->prepare($rowquery)) {

/* execute query */
$stmt->execute();

/* store result */
$stmt->store_result();

printf("%d", $stmt->num_rows - 1);

/* close statement */
$stmt->close();
}               

Can someone please help point me in the right direction? Thank you so much in advance! :)

Answer 1

If the ID field is the basis for your queue (ie higher the id higher the order in queue), then the query is as simple as counting the number of rows with id values <= to the user's id

SELECT count(id) FROM restaurant_guests WHERE id <= ?

Here ? represents the id value you are searching for.

Answer 2

Wait a minute. Are the ID auto-incremented? If only the guests with lower ID goes out of the queue first, then wouldn't it be better to just give:

answer = (the ID of user in question) - (lowest ID of the user in the queue) + 1

where the lowest ID of the user in the queue can be queried by:

SELECT ID from restaurant_guests ORDER BY ID LIMIT 1

At least, this approach will transfer a constant number of data from the DBMS in contrast with other approaches.