Is possible extract value from form and send to database service how a parameter (filter) for the select mysql)?

In my configuration, I try the next comand (BD mysql):
 
    SELECT user, name, lastname FROM Cordloc
    where user=<sql:param type="xs:string" select="/form/section-1/usuario"/>
 
This database service is conect to drowpdown, but when I incluye the sentence `"where user=<sql:param type="xs:string" select="/form/section-1/usuario"/>"`,
this it's not  working.
 
I try the show en drowdown name user, but filter with user login orbeon (in the table is same value "orbeon").
 
Please, can your help me with that.
 
Many thanks.

For those finding this thread through a search, since this question was cross-posted on Stack Overflow, and a follow-up has already been posted there, please refer to that discussion, and if you'd like please comment as well as on Stack Overflow:

http://stackoverflow.com/questions/43812144/extract-value-from-form-and-send-to-database-service-how-a-parameter-filter

Alex