Error in Trigger creation

[Syed Irtaza]

I am trying to create a custom id for my table in the following format


2 random alphabets - 00MaxID

for e.g: AA-001

I have tried writing a query for it but it is not working, this is my first time writing a trigger also writing a complex query such as this.

the following query gives me an error near "SET @ct = COUNT(cus_id);"

CREATE
TRIGGER `id_gen` AFTER INSERT
ON `testdb`.`customer`
FOR EACH ROW BEGIN

SELECT count(cus_id) INTO @ct
FROM customer;

IF @ct < 10 THEN
SET @cs_id = LPAD(@ct, 3, 0 );
ELSEIF @ct < 100
SET @cs_id = LPAD(@ct, 2, 0 );
ELSE
SET @cs_id = @ct;
END IF;

UPDATE customer
SET cus_id = CONCAT(CHAR(FLOOR(65 + RAND() * 26),FLOOR(65 + RAND() * 26)),'-',@cs_id)
WHERE cus_id = 'nil';

END;