Using joint statement with ifnull function MySQL

Question

I just want to replace the reference id with name from item table in the result as I showed in last table

1st table and Parent table

id	item	amount	tax	status
1	4	20	2	Y
2	5	15	1	N
3	6	5	0	N

2nd table and child table

id	item	p_id	amount	tax
1	1	1	10	1
2	2	2	10	1
3	3	1	15	1

3rd table

id	item
1	mobile
2	heater
3	mouse
4	electronic
5	software
6	papers

What I get from this code

SELECT IFNULL(child.item, parent.item) AS item, 
       IFNULL(child.amount, parent.amount) AS amount,
       IFNULL(child.tax, parent.tax) AS tax
FROM parent
LEFT JOIN child ON parent.id = child.p_id

item	amount	tax
1	10	1
2	10	1
3	15	1
5	15	1
6	5	0

What I want is

item	amount	tax
mobile	10	1
heater	10	1
mouse	15	1
software	15	1
papers	5	0

please help me to achieve this

Answer 1

Simply join the item table using the item ID you are already showing in your query:

SELECT
  i.item, 
  COALESCE(c.amount, p.amount) AS amount,
  COALESCE(c.tax, p.tax) AS tax
FROM parent p
LEFT JOIN child c ON c.p_id = p.id
JOIN item i ON i.id = COALESCE(c.item, p.item)
ORDER BY i.item;

(I am using COALESCE instead of IFNULL, because this is standard SQL. But you can stick with IFNULL, if you like it better.)