MySQL FULLTEXT not working

Add more data. By default MySQL will ignore any word that is in 50% or more of the rows in the table as it considers it would be a 'noise' word.

With very few rows in a table, it is common to hit this 50% limit often (ie. if you have two rows, every word is in at least 50% of the rows!).

There are two modes for MySQL Fulltext searching: natural language mode and Boolean mode. A restriction of natural language mode is " ... words that are present in 50% or more of the rows are considered common and do not match. Full-text searches are natural language searches if no modifier is given." And natural language is the default mode. This is documented in the Fulltext docs:

http://dev.mysql.com/doc/refman/5.0/en/fulltext-search.html

If you switch your query to using Boolean mode:

SELECT * FROM test WHERE MATCH(a) AGAINST('databases' IN BOOLEAN MODE)

Then the two rows are returned.

Boolean mode has its own restrictions, one common one being that it does not return its rows in order of relevance. Overall, it does offer more features and flexibility than natural language mode, so you'll probably end up using it.

If your application is going to rely heavily on fulltext searching you might want to consider more full-featured packages such as Lucene/Solr or Sphinx