SQL trigger INSERT AFTER - sql

Question

I am trying to setup a trigger in phpMyAdmin. have two tables, one parent, one child. Every time a new user in users is created I want to automaticly create a line in the permissions table with the (AI) generated id from users as user_id. (permissions.user_id is a foreigh key of users.id)
users:
id email password
--------------------------------------
1 eric#test.com sdgsdhdfhs
2 john#test.com dfgsdgdfhg
3 mary#test.com plkdfjvjvv
permissions:
index user_id allow_read allow_write allow_delete
-------------------------------------------------------------
1 1 1 0 1
2 2 1 1 1
3 3 0 0 0
I've tried (without success):
INSERT
INTO permissions
(user_id)
VALUES
(IDENT_CURRENT('users'))
and
INSERT
INTO permissions
(user_id)
VALUES
(##IDENTITY)

Answer 1

To access the data of the row that caused a trigger to be executed, you can use NEW and OLD aliases. For INSERT triggers only NEW is available. For DELETE triggers only OLD is available. In UPDATE triggers you can use both. They are used the same way as table aliases (e.g. NEW.id / OLD.id).
Given a parent and a child table as follows:
create table parent_table(
id int auto_increment primary key,
pdata varchar(50)
);
create table child_table(
id int auto_increment primary key,
parent_id int not null,
cdata varchar(50) default '',
foreign key (parent_id) references parent_table(id)
);
To insert a child row when a parent row is inserted:
create trigger insert_parent
after insert on parent_table
for each row
insert into child_table(parent_id)
values (new.id);
To delete all related child rows wehen a parent row is deleted:
create trigger delete_parent
before delete on parent_table
for each row
delete from child_table
where parent_id = old.id;
Demo: http://rextester.com/EOW74217
However a delete trigger is not necessary if you define your foreign key with ON DELETE CASCADE
foreign key (parent_id) references parent_table(id) on delete cascade
All related child rows will be deleted without a trigger when you delete the parent row.
Demo: http://rextester.com/CWB43482