Hello there i had to make some changes: improve performance for big tables always return de id of table even if it is not selected previously add another param (string list) to accept your own list of fields to search for. Result returns None if you entered to the form the first time, so you can "capture" this case and decide even show or not the result later in your view Use it like this

def search:
frmsearch,results = dynamic_search(db[tabla],'descripcion, fecha_solicitud')

if results <> None: 		
	return dict(tabla=tabla, frmsearch=frmsearch,  lista=results)			
else: 
	return dict(tabla=tabla, frmsearch=frmsearch)

The code

def dynamic_search(table,strfields):
	tbl = TABLE()
	selected = []
	ops = ['igual','no igual a','mayor que','menor que','comienza con','termina en','contiene']
	#print table.fields
	query = table.id > 0    
	for field in table.fields:
		if field in strfields:
			chkval = request.vars.get('chk'+field,None)
			txtval = request.vars.get('txt'+field,None)
			opval = request.vars.get('op'+field,None)
			row = TR(TD(INPUT(_type="checkbox",_name="chk"+field,value=chkval=='on')), \
		             TD(field),TD(SELECT(ops,_name="op"+field,value=opval)), \
		             TD(INPUT(_type="text",_name="txt"+field, _value=txtval)))
			tbl.append(row)
			if chkval:
				if txtval:					
					query &= build_query(table[field], opval,txtval)
					selected.append(table[field]) 
	
	if len(selected) > 0:
			selected.append(table.id) 
			results = db(query).select(*selected)
	else:
		results = None
	
	form = FORM(tbl,INPUT(_type="submit"))
	return form, results