So I was reading up on indexes and their implementation, and I stumbled upon this website that has a brief explanation of b-tree indexes:
http://20bits.com/articles/interview-questions-database-indexes/
The b-tree index makes perfect sense for indexes that are only on a single column, but let's say I create an index with multiple columns, how then does the b-tree work? What is the value of each node in the b-tree?
For example, if I have this table:
table customer:
id number
name varchar
phone_number varchar
city varchar
and I create an index on: (id, name, city)
and then run the following query:
SELECT id, name
FROM customer
WHERE city = 'My City';
how does this query utilize the multiple column index, or does it not utilize it unless the index is created as (city, id, name) or (city, name, id) instead?
