Unable to solve Java form of jdbc query with variables - jdbc

Question

sql3 = "select avg(eff),min(eff),max(eff) from(select ("+baseParam+"/"+denom+"))as eff from ras)as s"; This is query whose output i want.
When i execute the code i get the error stating check your mysql version for syntax. I am using string to store the name of columns. I want to find the efficienccy with respect to 2000 Job_Render i.e. efficiency for each job_render. But what i get is total efficiency of all job_render. when i use the sql syntax with their direct column names. I have commented that query too for the reference. I want to find efficiency of each job render with respect to their 2000 JOBID. Bottom line is i want to find efficiency of 2000 JOBID each whose formula is Job_Render/LC_Final+LC_Preview. I have stored Job_Render in String baseParam and sum of both LC in String Denom. Please help me out.
public class Efficiency {
static final String DB_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_CONNECTION = "jdbc:mysql://localhost:3306/";
static final String DB_USER = "root";
static final String DB_PASSWORD = "root";
static final String dbName = "raas";
public static void main(String[] args) {
try{
effFunc();
}
catch (Exception q){
q.getMessage();
}
}
static void effFunc() throws ClassNotFoundException,SQLException{
Connection conn = null;
// STEP 2: Register JDBC driver
Class.forName(DB_DRIVER);
// STEP 3: Open a connection
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_CONNECTION + dbName, DB_USER,
DB_PASSWORD);
System.out.println("Connected database successfully...");
String baseParam;
//String[] subParam ;
baseParam= "Job_Render";
String sql3="";
String denom="";
final String[] COL={ "LC_Final","LC_Preview"};
denom = "(" + COL[0] + "+" + COL[1] + ")";
Statement stmt = null;
stmt = conn.createStatement();
// sql3 = "select 'Efficiency' Field,avg(eff),min(eff),max(eff) from(select (Job_Render/(LC_Final+LC_Preview))as eff from ras)as s";
sql3 = "select avg(eff),min(eff),max(eff) from(select ("+baseParam+"/"+denom+"))as eff from ras)as s";
System.out.println(sql3);
//
try{
ResultSet res = stmt.executeQuery(sql3);
//System.out.println(res);
while(res.next()){
// String JobID = res.getString("JobID");
// System.out.println("Job ID : " + JobID);
String col1 = res.getString(1);
System.out.println(col1);
double avg = res.getDouble(2);
System.out.println("Average of eff is:"+avg);
double min = res.getDouble(3);
System.out.println("Min of eff is:"+min);
double max = res.getDouble(4);
System.out.println("Max of eff is:"+max);
}}
catch(Exception e){
e.getStackTrace();
System.out.println(e.getMessage());
}
}}

Answer 1

Your code runs the query sql1 which is the empty string,
String sql1="";
// sql1 = "select * from raas.jobs";
ResultSet res = stmt.executeQuery(sql1); // sql1 = ""
should be
ResultSet res = stmt.executeQuery(sql3);
Edit
Then to get the value(s)
String col1 = res.getString(1);
double avg = res.getDouble(2);
double min = res.getDouble(3);
double max = res.getDouble(4);