string sql = "select to_char(StartTime, ‘yyyy‘)||‘-‘|| to_char(StartTime, ‘mm‘)||‘-‘|| 
to_char(StartTime, ‘dd‘)||‘ ‘|| to_char(StartTime, ‘hh24‘)||‘:‘|| 
floor(to_char(StartTime, ‘mi‘)/15)*15 statime, sum(Count) as Counts from 
table where StartTime <= to_date(‘2016-11-29 18:00:00‘ ,‘YYYY-MM-DD hh24:mi:ss‘) 
group by to_char(StartTime, ‘yyyy‘)||‘-‘|| to_char(StartTime, ‘mm‘)||‘-‘|| 
to_char(StartTime, ‘dd‘)||‘ ‘|| to_char(StartTime, ‘hh24‘)||‘:‘|| 
floor(to_char(StartTime, ‘mi‘)/15)*15 order by statime";

string sql = "select to_char(StartTime, ‘yyyy‘)||‘-‘|| to_char(StartTime, ‘mm‘)||‘-‘||" +
             "to_char(StartTime, ‘dd‘)||‘ ‘|| to_char(StartTime, ‘hh24‘)||‘:‘|| " + 
             "floor(to_char(StartTime, ‘mi‘)/15)*15 statime, sum(Count) as Counts" + 
             " from table " + 
             "where StartTime <= to_date(‘2016-11-29 18:00:00‘ ,‘YYYY-MM-DD hh24:mi:ss‘) " +
             "group by to_char(StartTime, ‘yyyy‘)||‘-‘|| " + 
             "to_char(StartTime, ‘mm‘)||‘-‘|| to_char(StartTime, ‘dd‘)||‘ ‘|| " + 
             "to_char(StartTime, ‘hh24‘)||‘:‘|| floor(to_char(StartTime, ‘mi‘)/15)*15 order by statime";