MySQL create separate index for compound primary key or not

Question

I want to create table for store customer and daily statistic.

customer_stat table - (PK)on_date - (PK)customer_id - (PK)margin_id - (PK)agent_id

Search scenarios: - search by compound all primary keys - search by customer_id - search by margin_id - search by agent_id + margin_id

From scenarios above, should I create separate index for each key column or mysql already auto create index of each key for me?

Answer 1

I found solution to test this concept. I create table follow above structure with compound key, then test insert to database. Then check table structure in database, and found that:

MySQL create single index for compound primary key.

So I need to manual create separate index of each column for used in query by partial of key in compound keys.