Set auto-increments based on hospital ID - php

Question

My Company has multiple clients. Each client needs to have their own auto increment column.
For example, there are multiple hospitals that need to record their patients' records to my server. And each patient needs to have a reference number. Reference numbers are incrementing.
Here is what I want my table to look like
+-----------+-----------+-----------+----------+
| user_id | names | ref_no | hospital |
+-----------+-----------+-----------+----------+
| 1 |cholo wao | 1 | TMJ |
| 2 |royson ml..| 2 | TMJ |
| 3 |pascal va..| 3 | TMJ |
| 4 |mustafa s..| 1 | MBE |
| 5 |nassoro h..| 4 | TMJ |
| 6 |zunaida s..| 2 | MBE |
| 7 |hadija ma..| 3 | MBE |
| 8 |kulsum za..| 4 | MBE |
| 9 |zawadi ya..| 1 | MSA |
| 10 |khamis mo..| 5 | TMJ |
| 11 |saada hem..| 5 | MBE |
| 12 |mark zuck..| 6 | TMJ |
+-----------+-----------+-----------+----------+
As you have seen above the ref_no only increment based on the last insert ID of a previous Hosptial. I have been told that using MAX(hospital) can cause danger as more than one row may be inserted at a time.
summary QN
Which Query can I use to insert reference number based on the last ID of a particular hospital?

Answer 1

I have seen two solutions in SO about this, make a try
1st one
CREATE temporary table seq ( id int, seq int);
INSERT INTO seq ( id, seq )
SELECT user_id,
(SELECT count(*) + 1 FROM client c
WHERE hospital='TMJ') as seq
FROM client;
UPDATE client INNER join seq ON client.user_id = seq.id SET
client.ref_no = seq.seq;
2nd one
INSERT INTO
client( names, ref_no, hospital )
'cholo wao',SELECT MAX(ref_no) + 1 WHERE hospital='TMJ','TMJ' FROM
client;