MySQL Trigger After Insert, Action JOIN 2 tables - mysql

Question

I need to create a trigger (after insert on one table) on MySQL, but the action needs to join 2 tables, for inserting into a third table. My script below returns no error, but the row is not inserted into the third table.
The first table (on which the after-insert trigger should work):
Z_TAXO
ID term_ID taxo_name
1 1 dept
2 2 staff
3 4 course
4 5 dept
The second table to be joined in the trigger:
Z_TERM
term_ID name
1 Engineering
2 Andy
4 Metallurgy
5 Business
6 Arts
The third table. If the Z_TAXO table has a new row with taxo_name = "dept", the row (joined with table Z_TERM) needs to be inserted into this table:
Z_DEPTS
ID dept_name
1 Engineering
4 Business
I created a trigger:
delimiter //
CREATE TRIGGER TRG_NEW_DEPT
AFTER INSERT ON Z_TAXO
FOR EACH ROW
BEGIN
DECLARE _dept_ID bigint(20);
DECLARE _dept_name varchar(200);
IF Z_TAXO.taxo_name = "DEPT" THEN
BEGIN
SELECT Z_TAXO.ID INTO _dept_ID FROM Z_TAXO, Z_TERM
WHERE Z_TAXO.ID = new.Z_TAXO.ID AND Z_TAXO.term_ID = Z_TERM.term_ID;
SELECT Z_TERM.name INTO _dept_name FROM Z_TERM, Z_TAXO
WHERE Z_TAXO.term_ID = Z_TERM.term_ID AND Z_TAXO.ID = new.Z_TAXO.ID;
INSERT INTO Z_DEPTS (ID, dept_name) VALUES (_dept_ID, _dept_name);
END;
END IF;
END//
delimiter ;
Then inserted a row to the Z_TAXO table:
INSERT INTO Z_TAXO (ID, term_ID, taxo_name) VALUES (5, 6, "dept");
Expecting to have this new row in table Z_DEPTS:
ID dept_name
5 Arts
But when I select * from Z_DEPTS, the result is still:
ID dept_name
1 Engineering
4 Business
What can be wrong? I can't modify the design of the tables, because they came from a wordpress Plugin. Thanks in advance!

Answer 1

Couple of comments about your code. 1) When using new. qualifiers you don't further qualify with the table name so new.z_taxo.id is invalid andd should simply be new.id 2) You don't need a begin..end block in a mysql if statement 3) if just doesn't make sense referring to the table z_taxo in your select stataments - a simple insert select will do.
try
drop trigger if exists trg_new_dept;
delimiter //
CREATE TRIGGER TRG_NEW_DEPT
AFTER INSERT ON Z_TAXO
FOR EACH ROW
BEGIN
INSERT INTO Z_DEPTS (ID, dept_name)
select term_id, name
from z_term
where term_id = new.term_id;
END//
delimiter ;