MySQL Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use

I am getting the error as:

Message = "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '=0) OR (inq1.event_id in())) AND  (('--Select--'='--Select--') OR (inq.inquiry_s' at line 1"

 queryStr = "SELECT distinct  inq.inquiry_id,inq.source,inq.contact_name,inq.contact_name2,inq.email,inq.email1,inq.email2,inq.email3,inq.email4,inq.email5,inq.website,inq.website1,inq.contact_number,inq.telphone,inq.fax, inq.mobile, inq.product, inq.designation, inq.designation2, inq.address,inq.reason,inq.interested_in,inq.company,cat.category,country.country_name,inq.date,inq.inquiry_status,log.name " + appquery2 + " FROM crm_inquiry_perticipant inq  " +
                   " INNER JOIN crm_login log ON inq.inquiry_owner=log.log_id " +
                   "INNER JOIN crm_category cat ON inq.cat_id=cat.cat_id INNER JOIN crm_countries country ON inq.country=country.country_id  " +
                    "INNER JOIN crm_inquiry_event_assigned inq1 on inq.inquiry_id=inq1.inquiry_id " +
                    "INNER JOIN crm_event event on inq1.event_id=event.event_id " +
                  " WHERE   " +
                  " (( " + owner + "=0) OR (inq.inquiry_owner=" + owner + ")) AND " +
                   "(( " + category + "=0) OR (inq.cat_id=" + category + ")) AND " +
                    " ((" + country + "=0) OR (inq.country=" + country + ")) AND " +
                     " ((" + agent + "=0) OR (inq.agent_id=" + agent + ")) AND  " +
                     " ((" + queryEventIDs + "=0) OR (inq1.event_id in(" + queryEventIDs + "))) AND  " +
                     //     "inq1.event_id in(" + queryEventIDs + ") AND " +
                     "(('" + status + "'='--Select--') OR (inq.inquiry_status='" + status + "')) AND " +
                      " (('" + StartDateString + "'='') OR (inq.date BETWEEN '" + StartDateString + "' AND '" + EndDateString + "'))  " +                     
                     appquery + prodquery + " Order By inq.inquiry_id desc  ";

I am trying to export the details from start date to end date.I am not getting the result but if i am commenting on below line, iam getting the details from start to end date.Whats wrong with the query.

 " ((" + queryEventIDs + "=0) OR (inq1.event_id in(" + queryEventIDs + "))) AND  " +