Substring, Count, and Concat in a Before Insert Trigger? - mysql

Question

I have a dilemma where I need to have a MySQL database create a customer number based on the first 3 characters of a new client name entered and to append an incremenenting value. For example:
Table clients:
+----+----------------------------------------------+--------------+
| id | clientName | clientNumber |
+----+----------------------------------------------+--------------+
| 1 | Accelerated Learning | ACC00 |
| 2 | Acceleration Systems | ACC01 |
| 3 | Acme,Inc. | ACM00 |
Normally I would do this in the submission form on the front end, but for reasons unexplained, the spec wants this handled by the DB. I'm trying to write something like this, but can't get it right:
Trigger:
CREATE DEFINER = CURRENT_USER TRIGGER `crmdev`.`clients_BEFORE_INSERT` BEFORE INSERT ON `clients` FOR EACH ROW
BEGIN
DECLARE prefix varchar(3);
DECLARE suffix INT(3);
SET prefix = SUBSTRING(NEW.clientName,1,3);
SET suffix = (
SELECT COUNT(*),SUBSTRING(clientName,1,3) = prefix + 1;
SET NEW.clientNumber = CONCAT(prefix,suffix);
END
Thanks in advance for help/guidance!

Answer 1

You have syntax errors in the suffix assignment. You're missing the FROM and WHERE clauses, and you need to add 1 to the count, not to prefix.
SET suffix = (
SELECT COUNT(*)+1
FROM clients
WHERE SUBSTRING(clientName,1,3) = prefix);

Answer 2

Here's the finished product if helpful to others & thanks to Barmar:
Trigger:
DECLARE prefix varchar(3);
DECLARE suffix INT(3);
SET prefix = SUBSTRING(NEW.clientName,1,3);
SET suffix = (
SELECT COUNT(*)+1
FROM clients
WHERE SUBSTRING(clientName,1,3) = prefix);
SET NEW.clientNumber = UPPER(CONCAT(prefix,LPAD(suffix,3,0)));