Limiters will vary from database to database.
Use parentheses to narrow or expand your search results. First, keywords and operators within parentheses are processed. Next, keywords and operators outside parentheses are processed.
* (baseball or football) AND (artificial intelligence)
Per the Z39.50 standard, Boolean operators AND and NOT are processed before OR if parentheses are not used.
* Baseball OR football AND artificial intelligence will be processed as baseball OR (football AND artificial intelligence).