MySQL查询和优化数据库

Question

I have a project i need to make for school. It's a game made in Javafx based on munchkin (board game).

We have a hero, this hero will defeat monsters in a room, and each monster defends a treasure (i'm seeing it as the monster's loot like in a mmorpg). Now i'm not sure about the link between monsters and treasures aswell. Each treasure has 0 or 1 monster. Each monster atleast has one treasure, can be multiple aswell. The teacher said to use an extra table for this (Treasure_has_Monsters) in my case. I'm not sure the references are correct though...

My database at the moment: Database Design

Now the problem i'm having is the following. I need to get a list from all the treasures a monster has . And i could query the treasure_has_monster table and get all the id's of treasures and then create a query to get all the treasures with the id's.

Questions:

• Is there a way to do this in one query?
• Is the reference between Treasures and Monsters ok?

Answer 1

You can try making a simple query like:

SELECT t.name
FROM treasure_has_monster thm
INNER JOIN trasures t ON (thm.trasure_id = t.id)
WHERE thm.monster_id = YOUR_MONSTER_ID

Answer 2

According to your schema, you could try:

select t.* from Treasures t
join Treasures_has_Monsters tm on tm.Treasure_id=t.id
where Monster_id=?

where? is the monster id you want to list the treasures for.

Answer 3

No reason to join both tables together. You could use a simple inner query.

SELECT * FROM Treasures
WHERE id IN (SELECT treasure_id from Treasures_has_Monsters
             WHERE monsterid = <MID>);

replace <MID> with the monster id you want to get