Facing performance issue while iterating through the ResultSet of an SQL query with cursor expressions.
SQL query(example)
select id, name , cursor (select id,name from subject ) as cusr1 from student
This is how I am retrieving the cursor in java
statement = connection.createStatement();
resultSet=statement.executeQuery(query);
while (resultSet.next()) { //Read every row
int columnCount = resultSet.getMetaData().getColumnCount();
for (int column = 1; column <= columnCount; column++) { //Read every column
String columnName = resultSet.getMetaData().getColumnName(column);
Object value = resultSet.getObject(columnName);
if (value != null) {
System.out.println("Value Not Null");
if(value instanceof ResultSet){
System.out.println("Success");
ResultSet rs1=(ResultSet)value;
while(rs1.next()){
String name=rs1.getString("name");
System.out.println("Name is "+name);
Long id=rs1.getLong("id");
System.out.println("Id is "+id);
}
}
}
}
}
The execution time of the query is very less compared to the processing time of the resultSet (iterating through the same ,getting the cusror data etc).
Am I doing anything wrong here?Is there any way to improve the performance?
Related
I am currently writing a simple Java app that reads information from an XLS file and then enters it in the database. Since that XLS does have duplicated records, I do a simple check if the entry in the XLS file already exists in the database. Here is my code:
public static void addResult(ArrayList<ArrayList<String>> listResults)
{
try
{
openDatabase();
stmt = c.createStatement();
for (int i = 0; i < listResults.size(); i++)
{
PreparedStatement stm = c.prepareStatement("SELECT player_name FROM results WHERE player_name=?;");
stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
System.out.println(stm);
ResultSet rs = stm.executeQuery();
if (rs.getRow() <= 0)
{
String typeOfPlay = new String();
if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Simple"))
{
typeOfPlay = "single";
}
else if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Double"))
{
typeOfPlay = "double";
}
stm = c.prepareStatement("INSERT INTO results (player_name, school_id, " + typeOfPlay + ", tournament_id) "
+ "VALUES(?,?,?,?);");
stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
stm.setString(2, listResults.get(i).get(ReadResultsFile.SCHOOL_ID));
stm.setInt(3, Integer.parseInt(listResults.get(i).get(ReadResultsFile.SCORE)));
stm.setString(4, "1");
stm.executeUpdate();
}
else
{
String typeOfPlay = new String();
if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Simple"))
{
typeOfPlay = "single";
}
else if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Double"))
{
typeOfPlay = "double";
}
stm = c.prepareStatement("UPDATE results SET " + typeOfPlay + "=? WHERE player_name=?;");
stm.setString(1, typeOfPlay);
stm.setString(2, listResults.get(i).get(ReadResultsFile.SCORE));
stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
System.out.println(stm);
stm.executeUpdate();
}
}
closeDatabase();
}
catch (Exception e)
{
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
}
The problem that arises is that the rs.getRow() function always returns -1. I tried running the SELECT query directly in the database tool and the query returns the player_name column if there is already a similar entry existing. It unfortunately do the same in Java.
I am unsure what to do at this point.
Thank you for any hint!
getRow will not work as per the javadocs
Retrieves the current row number. The first row is number 1, the second number 2, and so on.
and
A ResultSet cursor is initially positioned before the first row; the
first call to the method next makes the first row the current row
Usually use
while (rs.next ()) {....
I have a jTable with 4 columns and 6 rows. i want to iterate thru the rows picking up the values of column index0 which is my ID column and passing it to a count sql query. i have written the below code which is not working because i haven't figured out how to pass the columns values after iterating through the table.
can someone please let me know what am doing wrong on my code please.
for (int row = 0; row > jTable2.getRowCount(); row++){
for (int col =0; col > jTable2.getColumnCount(); col ++)
try{
DefaultTableModel model = (DefaultTableModel)jTable2.getModel();
String selected = model.getValueAt(row, col+1).toString();
String sql = "select COUNT(COURSEBOOKED) from APP.BOOKCOURSE where COURSEBOOKED = '"+selected+"'";
try(Connection con = DriverManager.getConnection("jdbc:derby:MTD","herbert","elsie1*#");
PreparedStatement pst = con.prepareStatement(sql);) {
ResultSet rs = pst.executeQuery();
while(rs.next()){
String Sum = rs.getString("COUNT(COURSEBOOKED)");
System.out.println(Sum);
if (rs.wasNull()){
System.out.println("No record found");
}
}
}
catch(SQLException e){
}
}
catch(Exception e){
}
}
This is the final code that came up with after the changes.
String sql = "select COUNT(COURSEBOOKED) as count from APP.BOOKCOURSE where COURSEBOOKED =?";
try(Connection con = DriverManager.getConnection("jdbc:derby:MTD","herbert","elsie1*#");
PreparedStatement pst = con.prepareStatement(sql);){
for(int row = 0; row < jTable2.getRowCount(); row++){
DefaultTableModel model = (DefaultTableModel)jTable2.getModel();
String selected = model.getValueAt(row, 1).toString();
pst.setString(1, selected);
try(ResultSet rs = pst.executeQuery();){
while (rs.next()){
String Sum = rs.getString("count");
System.out.println(Sum);
}
}
}
}
catch(SQLException e){
JOptionPane.showMessageDialog(this, e);
}
Which brings me to my next question. AM not sure whether i should start a new thread for it or continue on this one. My challenge is that i now want to append an addition column to the existing 4 columns on the current jTable2 and display the values of the above query. to add a new column i have used this code,
TableColumn c = new TableColumn();
c.setHeaderValue("Training accomplished");
model.addColumn(c);
This adds the column but populates its with values from column index0. how do i get the new added column to be populated by the values held in Sum from the query above.
You should use something like below. Note that I haven't tested this code so far, so you might need to debug it. Also check the comments on your question.
String sql = "select COUNT(COURSEBOOKED) as count from APP.BOOKCOURSE where COURSEBOOKED = ?";
try(
Connection con = DriverManager.getConnection("jdbc:derby:MTD","herbert","elsie1*#");
PreparedStatement pst = con.prepareStatement(sql);){
for (int row = 0; row < jTable2.getRowCount(); row++){
DefaultTableModel model = (DefaultTableModel)jTable2.getModel();
String selected = model.getValueAt(row, 0).toString();
pst.setString(1, selected);
ResultSet rs = pst.executeQuery();
while(rs.next()){
String Sum = rs.getString("count");
System.out.println(Sum);
if (rs.wasNull()){
System.out.println("No record found");
}
}
}
}
catch(SQLException e){
}
catch(Exception e){
}
how could i subtract a value based on the input on the text field directly to my database?
and how can i execute two queries at the same time i tried doing this but i had no luck
heres the code i am trying to execute
String sql1 = "select seat from passenger_details where seat = '"+seats+"'";
resultset = statement.executeQuery(sql1);
int count = 0;
while(resultset.next()) {
count = count + 1;
}
if(cc.equals("")||add.equals("")) {
JOptionPane.showMessageDialog(null,"Please Complete the form");
} else {
sql1 = "INSERT INTO passenger_details(fname,lname,gender,address,cc_no,bank_name,no_of_tickets,seat) VALUES('"+fnm+"','"+lnm+"','"+gnd+"','"+add+"','"+cc+"','"+bank+"','"+tckts+"','"+seats+"'),('"+fnm+"','"+lnm+"','"+gnd+"','"+add+"','"+cc+"','"+bank+"','"+tckts+"','"+seats2+"'),('"+fnm+"','"+lnm+"','"+gnd+"','"+add+"','"+cc+"','"+bank+"','"+tckts+"','"+seats3+"'),('"+fnm+"','"+lnm+"','"+gnd+"','"+add+"','"+cc+"','"+bank+"','"+tckts+"','"+seats4+"'),('"+fnm+"','"+lnm+"','"+gnd+"','"+add+"','"+cc+"','"+bank+"','"+tckts+"','"+seats5+"')";
String sql2 = "Update flight_details set seats_avail= seats_avail-'"+tckts+" Where route_name = '"+dest+"'";
statement.addBatch(sql1);
statement.addBatch(sql2);
statement.executeBatch();
JOptionPane.showMessageDialog(null,"Sucess");
}
I need to fill a Swing table with some data from MySQL DB. The problem is that the table does not display all the columns (i.e. a.aircraftType and b.aircraftCategory). In Debug mode I checked that the query returns correct data. So, why finally some columns are not displayed?
private JTable tbArrivals;
private QueryTableModelFS mdArrivals;
mdArrivals = new QueryTableModelFS();
tbArrivals = new JTable(mdArrivals);
private void fillArrivals() {
mdArrivals.setHost(url); mdArrivals.setDB(db); mdArrivals.setLogin(login); mdArrivals.setPassw(passw);
String query;
query = "SELECT a.id,a.flightNum_arr,a.from_ICAO,a.ETA,a.pkId,a.aircraftType,b.aircraftCategory " +
"FROM flightschedule a, aircrafts b " +
"WHERE a.aircraftType = b.aircraftType;";
mdArrivals.setQuery(query);
}
public void setQuery(String query) {
cache = new Vector();
try {
// Execute the query and store the result set and its metadata
Connection con = getConnection();
Statement statement = con.createStatement();
ResultSet rs = statement.executeQuery(query);
ResultSetMetaData meta = rs.getMetaData();
colCount = meta.getColumnCount();
// Rebuild the headers array with the new column names
headers = new String[colCount];
for (int h = 1; h <= colCount; h++) {
headers[h - 1] = meta.getColumnName(h);
}
while (rs.next()) {
String[] record = new String[colCount];
for (int i = 0; i < colCount; i++) {
record[i] = rs.getString(i + 1);
}
cache.addElement(record);
}
fireTableChanged(null);
rs.close();
if (con.getAutoCommit() != false) {
con.close();
}
} catch (Exception e) {
cache = new Vector();
e.printStackTrace();
}
}
I can't tell what how your TableModel works (it looks like you might be using the DefaultTableModel), but I would suggest using Vectors instead of Arrays to get the data from your ResultSet. Right now your code is very confusing. In one loop you are using (i - 1) to access the data. In the next loop you are using (i + 1). I know the reason is because Arrays are 0 based and the ResultSet is 1 based.
When you use a Vector your loops can just start with 1 and then you just use the addElement() method to add the data to the Vector so your code is not concerned with matching indexes.
See Table From Database Example in Table From Database.
I have tried different ways to get the row count in java JDBC, nut none seemed to be giving the correct result. Is there anything wrong that I am doing ?
Even though the customer table is empty and I should be getting the rowcount as 0, I don't understand why I get a non zero rowcount value.
Method 1 -
query = "SELECT * FROM customer WHERE username ='"+username+"'";
rs = stmt.executeQuery(query);
ResultSetMetaData metaData = rs.getMetaData();
rowcount = metaData.getColumnCount();
Method 2 -
query = "SELECT * FROM customer WHERE username ='"+username+"'";
rs = stmt.executeQuery(query);
rowcount = rs.last() ? rs.getRow() : 0;
See this snippet of code:
import java.io.*;
import java.sql.*;
public class CountRows{
public static void main(String[] args) {
System.out.println("Count number of rows in a specific table!");
Connection con = null;
int count = 0;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctutorial","root","root");
try {
Statement st = con.createStatement();
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter table name:");
String table = bf.readLine();
ResultSet res = st.executeQuery("SELECT COUNT(*) FROM "+table);
while (res.next()){
count = res.getInt(1);
}
System.out.println("Number of row:"+count);
}
catch (SQLException s){
System.out.println("SQL statement is not executed!");
}
}
catch (Exception e){
e.printStackTrace();
}
}
}
This the way I use to get the row count in Java:
String query = "SELECT * FROM yourtable";
Statement st = sql.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY );
ResultSet rs = st.executeQuery(query);
int rows = 0;
rs.last();
rows = rs.getRow();
rs.beforeFirst();
System.out.println("Your query have " + rows + " rows.");
When you working with JDBC that does not support TYPE_FORWARD_ONLY use this method to get rowcount.
Statement s = cd.createStatement();
ResultSet r = s.executeQuery("SELECT COUNT(*) AS rowcount FROM TableName");
r.next();
int count = r.getInt("rowcount");
r.close();
System.out.println("MyTable has " + count + " row(s).");
You can Get Row count using above method.
Thanks..
In Android, having no results returns an error. So check this case before incrementing count in while(resultset.next())
if(resultset!=null)
{
//proceed with incrementing row count function
}
else
{
// No resultset found
}
Just iterate and count
ResultSet result = sta.executeQuery("SELECT * from A3");
int k=0;
while(result.next())
k++;
System.out.print(k); //k is the no of row
As method name specifies metaData.getColumnCount() will return total number of columns in result set but not total no of rows (count).