adder - 11:58 am on Feb 13, 2013 (gmt 0)
How big is the database and how many columns do you have? If it's huge, you might want to create a system that indexes your main database and saves the searchable data in another database.
Then your search script runs on the index database and simply references the entries from the main database. In other words, your index database would only have id, name, title, content columns (and the item's id is identical to the id on the main database).
Otherwise, if you do "select * from tablename" on a huge database, as jatar_k said, it will be hellishly resource-intensive.