Instr() function on drupal I need a funtionality for search tags from a textarea (drupal form), I make it from sql, then, mysql have this function:
https://dev.mysql.com/doc/refman/5.0/en/string-functions.html
I believe that oracle/pql does have same function.

select * from cms_tags ct 
 where instr('Americana Abstract Art Art Antique Jewelry Antique Jewelry Jewelry', ct.name);


How can I use that query in drupal way? using db_select() or something else.
A plain db_query() might be easier for this particular query, but if you want to use db_select() you can make use of the SelectQuery::where() method:

$string = 'Americana Abstract Art Art Antique Jewelry Antique Jewelry Jewelry';

$query = db_select('cms_tags', 'ct')
  -&gt;fields('ct')
  -&gt;where('INSTR(:string, ct.name)', array(':string' =&gt; $string));