How do FULLTEXT INDEXES on multiple columns work?

Question

When adding a FULLTEXT INDEX on 3 columns, does that add 1 single index on 3 columns, or does it add 3 separate indexes?

I ask this, because at the moment I\'m using

Answer 1

Glancing over the manual for CREATE FULLTEXT INDEX, it indicates that you are able to specify multiple columns by repeating the column_name as such:

CREATE FULLTEXT INDEX ON table_name (column_name1 [...], column_name2 [...]) ...

Given this information, I would assume it creates a single index across 3 columns. Further, I'm assuming that it works under the left-to-right rule with regards to composite indexes (I would verify this by checking the execution plan for the following statements). Therefore, a composite index on (col1, col2, col3) would have to be selected in that order for it to be used (SELECT col1, col2 ...). If you were to call col2 it would not use the index.