combining two columns in to one using multiple line triggers in mysql - mysql

Question

The following is my table schema:
+--------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+--------------+------+-----+---------+-------+
| LicenceID | int(11) | NO | PRI | NULL | |
| PassingRTO | varchar(4) | NO | | NULL | |
| DLNO | int(15) | YES | | NULL | |
| DateOfIssue | date | NO | | NULL | |
| DateOfExpiry | date | NO | | NULL | |
| COV | varchar(6) | NO | | NULL | |
| DateOfBirth | date | NO | | NULL | |
| BloodGroup | varchar(3) | YES | | NULL | |
| FullName | varchar(50) | NO | | NULL | |
| FathersName | varchar(50) | YES | | NULL | |
| Address | varchar(150) | NO | | NULL | |
| PinCode | int(6) | NO | | NULL | |
| IssuingAuth | int(7) | NO | | NULL | |
| IDIA | int(11) | YES | | NULL | |
| Valid | tinyint(4) | NO | | NULL | |
+--------------+--------------+------+-----+---------+-------+
What i want to do is When i insert a new row, i want my DLNO as PassingRTO+LicenceID and IDIA as PassingRTO+IssuingAuth.
I tried the same using -
create trigger insert_combined
after insert on LicencesDB
for each row
BEGIN
set new.IDIA = concat(new.PassingRTO, new.IssuingAuth);
set new.DLNO = concat(new.PassingRTO,new.LicenceID);
END;
but gives me an error as -
ERROR 1362 (HY000): Updating of NEW row is not allowed in after
trigger ERROR 1193 (HY000): Unknown system variable 'DLNO' ERROR 1064
(42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use
near 'END' at line 1
Now I have two questions can we do this using multiple lines in triggers? and can't we combine two columns at the time of creating the table itself? like col1 = col2 + col3?
Thanks in advance!

Answer 1

don;t forget to change the DELIMITER
DELIMITER $$
create trigger insert_combined
after insert on LicencesDB
for each row
BEGIN
set new.IDIA = concat(new.PassingRTO, new.IssuingAuth);
set new.DLNO = concat(new.PassingRTO,new.LicenceID);
END $$
DELIMITER ;

Answer 2

Please check this link on mysql triggers. When you want to make an update on the current row being entered you can't use the after clause.
check http://dev.mysql.com/doc/refman/5.1/en/create-trigger.html
When you want to use
SET NEW.col_name = value
in your trigger, please note that you CANNOT use this with the AFTER the action, and must use it BEFORE the action.
Therefore, this will work:
CREATE TRIGGER sdata_insert BEFORE INSERT ON `sometable`
FOR EACH ROW
BEGIN
SET NEW.guid = UUID();
END
;
And this will NOT work:
CREATE TRIGGER sdata_insert AFTER INSERT ON `sometable`
FOR EACH ROW
BEGIN
SET NEW.guid = UUID();
END
;
Also you can probably do it in the code itself before even entering into the database.