Changing NPC Stats In One Zone

[Aquaojo]

So far I have figured out how to pull the mobs from Kael using this query:

SELECT * FROM spawn2 JOIN spawngroup ON spawngroup.id = spawn2.spawngroupID
JOIN spawnentry ON spawngroup.id = spawnentry.spawngroupID
JOIN npc_types ON spawnentry.npcID = npc_types.id
WHERE spawn2.zone LIKE 'kael'

Admittedly I am just learning about JOIN and figuring out how all this works...So anyone able to tell me how I would now add in:

UPDATE npc_types SET HP = HP * 0.75

in order to decrease all NPC HP in Kael by 25%??

I know it has to be right in front of my face, but I am missing it for some reason...

Thanks everyone!!