On systems with hundreds of thousands of records, these two queries take 17 seconds. Can anyone see a way to optimize them without changing the results? It's a strange query which was modified in the past to add the >0 section because sqlserver was returning errors without out it.

lcParent_Id = ALLTRIM(NVL(parent_id,''))  && 
lcChild_Id = ALLTRIM(NVL(child_id,''))

TEXT TO lcSQL NOSHOW PRETEXT 15 TEXTMERGE

      SELECT tw.* FROM tow AS tw

       INNER JOIN

            (SELECT inhistory.child_id FROM inhistory

             WHERE  inhistory.child_id = '<<lcchild_id>>'

             OR inhistory.parent_id = '<<lcchild_id>>'

             OR (LEN(inhistory.child_id)>0 AND inhistory.child_id = '<<lcParent_Id>>')

             OR (LEN(inhistory.parent_id)>0 AND inhistory.parent_id = '<<lcParent_Id>>')) qry1

      ON tw.child_id = qry1.child_id WHERE tw.towid > 0 AND tw.vehi_id > 0 AND canccode='    '

ENDTEXT

IF SQLProc("SP",m.lcSQL,,,"cTowCT") > 0 && Return any Tow records

      TEXT TO lcSQL2 NOSHOW PRETEXT 15 TEXTMERGE

            SELECT qry2.towid, vh.* FROM vhtable as vh 

      INNER JOIN

            (<<m.lcSQL>>) qry2

            ON vh.vehi_id = qry2.vehi_id ORDER BY vh.vehi_id

      ENDTEXT

      IF SQLProc("SP",m.lcSQL2,,,"cvhtableIn") > 0 && Return the vhtable Records

            SELECT cvhtableIn

      ENDIF

ENDIF