How to use an IF statement in a MYSQL Trigger? - mysql

Question

Trying to create a trigger that will look for two conditions and update an audit table with those. The trigger works on a customers table and looks for an update to phone number and/or credit limit. The audit table will have a column that show's which field was update or if both were updated.
Here's what I have so far (update with code from below) same error:
#Here's the audit table I created:
create table cust_audit(customerNumber INT, customerName varchar(50),
phone varchar(50), creditLimit dec(10,2),
last_update timestamp, `user` varchar(30),
row_value varchar(20), fields_changed,
varchar(30));
Delimiter $$
CREATE TRIGGER cust_upd_old
AFTER UPDATE
ON customers
FOR EACH ROW
Begin
INSERT INTO audit_table(customerNumber,
customerName,
phone,
creditLimit,
last_update,
`user`,
row_value,
fields_changed)
VALUES (OLD.customerNumber,
OLD.customerName,
OLD.phone,
OLD.creditLimit,
now(),
current_user(),
'before update',
CASE WHEN NEW.phone = OLD.phone THEN 'creditLimit'
WHEN NEW.creditLimit = OLD.creditLimit THEN 'phone number'
ELSE 'both'END);
END $$
DELIMITER ;
The trigger will run but when I try to run an update statement the update fails with code Error Code: 1054. Unknown column 'customerNumber' in 'field list' but the select statement will work so it's some error with the trigger I think. USING MYSQL 8.0.21
update customers set phone = '2128822470' where customerNumber = 181;
select * from customers where customerNumber = 181;

Answer 1

Can be simplified to
CREATE TRIGGER cust_upd_old
AFTER UPDATE
ON customers
FOR EACH ROW
INSERT INTO audit_table(customerNumber,
customerName,
phone,
creditLimit,
last_update,
`user`,
row_value,
fields_changed)
VALUES (OLD.customerNumber,
OLD.customerName,
OLD.phone,
OLD.creditLimit,
now(),
current_user(),
'before update',
CASE WHEN NEW.phone = OLD.phone THEN 'creditLimit'
WHEN NEW.creditLimit = OLD.creditLimit 'phone number'
ELSE 'both' END);