How to update data using two tables - mysql

Question

I have two tables gains and final_gains.
I'm wondering how I could calculate the sum of two columns and insert it into a different table...I need to be using a WHERE clause which would be inside runescape_name inside the gains table.
Like so
hitpoints_end_exp - hitpoints_starting_exp,
magic_end_exp - magic_starting_exp,
range_end_exp - range_starting_exp
And insert the result into final_gains.hp_gained, final_gains.magic_gains and final_gains.range_gained
Here are my two tables
gains
+------------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+-------------+------+-----+---------+-------+
| runescape_name | varchar(12) | NO | PRI | NULL | |
| hitpoints_starting_exp | int(50) | NO | | NULL | |
| magic_starting_exp | int(50) | NO | | NULL | |
| range_starting_exp | int(50) | NO | | NULL | |
| hitpoints_end_exp | int(50) | NO | | NULL | |
| magic_end_exp | int(50) | NO | | NULL | |
| range_end_exp | int(50) | NO | | NULL | |
+------------------------+-------------+------+-----+---------+-------+
final_gains
+----------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------+-------------+------+-----+---------+-------+
| runescape_name | varchar(12) | NO | PRI | NULL | |
| hp_gained | int(50) | NO | | NULL | |
| magic_gained | int(50) | NO | | NULL | |
| range_gained | int(50) | NO | | NULL | |
+----------------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
Sorry If I'm unclear, trying to explain the best as I can, I hope I'm clear enough

Answer 1

Use an INSERT, SELECT like this:
INSERT INTO final_gains (runescape_name, hp_gained, magic_gains, range_gained)
SELECT runescape_name,
hitpoints_end_exp - hitpoints_starting_exp,
magic_end_exp - magic_starting_exp,
range_end_exp - range_starting_exp
FROM gains;
In order to avoid duplicate keys:
INSERT INTO final_gains (runescape_name, hp_gained, magic_gains, range_gained)
SELECT runescape_name,
hitpoints_end_exp - hitpoints_starting_exp,
magic_end_exp - magic_starting_exp,
range_end_exp - range_starting_exp
FROM gains
ON DUPLICATE KEY
UPDATE hp_gained = hitpoints_end_exp - hitpoints_starting_exp,
magic_gains = magic_end_exp - magic_starting_exp,
range_gained = range_end_exp - range_starting_exp;
This is untested code, but should be close.
Note: I removed the first suggestion as it s not applicable to these table definitions. runescape_name is primary key in table final_gains so it has to be inserted/assigned as well.