Get max value sql in Java

Get max value sql in Java - java

*I don't get value of max in function other. Value return is "0". I trying but not success :(
Image
public int PriceMax(int manhom){
Connection conn = this.connect();
int max = 0;
if(conn != null){
try {
java.sql.Statement statement = conn.createStatement();
String sql = "SELECT AVG(GiaSP) from tbsanpham where manhom = '"+manhom+"'";
ResultSet rs = statement.executeQuery(sql);
max = rs.getInt(sql);
} catch (SQLException ex) {
Logger.getLogger(CSDL.class.getName()).log(Level.SEVERE, null, ex);
}
}
return max;
}
Help!!!
int manhom = cbbNhomSanPham.getSelectedIndex();
CSDL csdl = new CSDL();
int max = csdl.PriceMax(manhom);
JOptionPane.showMessageDialog(null, "Nhóm sản phẩm: '"+cbbNhomSanPham.getName()+"' \nPrice max: '"+max+"' ");

You're not using it as it should be.
First of all, you use AVG but want MAX so change it to MAX(GiaSP). Second, you must use rs.next() to have your cursor go to the first row and then get information from it.
java.sql.Statement statement = conn.createStatement();
String sql = "SELECT MAX(GiaSP) from tbsanpham where manhom = '"+manhom+"'";
ResultSet rs = statement.executeQuery(sql);
if (rs.next()) {
max = rs.getInt(1);
}

ResultSet rs = stmt.executeQuery("select MAX(GiaSP) as maxGiaSP from tbsanpham where manhom = '"+manhom+"'");
if (rs.next())
{
int w = rs.getInt("maxGiaSP ");
// just return this int
}

Related

How to get all the prices from a particular column add them and print them

I have a column name(selling price) in a database which contains all the prices of a product now what i want is to add all the selling prices and display the total selling price.
for example: Selling price column contains
Selling price
-------------
580
580
20
i want to add all the selling prices and display the total in the case the total will be 1180.
try {
Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost/customerinfo", "root", "");
Statement st = con.createStatement();
ResultSet rs;
String mysqlQuery = "SELECT `sellingprice` FROM cust_info";
rs =st.executeQuery(mysqlQuery);
while(rs.next()) {
String total = rs.getString("sellingprice"); // getting all the selling prices
//converting to integer
int totalValue = Integer.parseInt(total);
// what logic should goes here....
System.out.println(totalValue);
}
}catch(Exception e) {
System.out.println(e.getMessage());
}

You can just use SUM in the query like in the comment above or you can do the following:
try {
Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost/customerinfo", "root", "");
Statement st = con.createStatement();
ResultSet rs;
String mysqlQuery = "SELECT `sellingprice` FROM cust_info";
rs =st.executeQuery(mysqlQuery);
int totalValue = 0;
while(rs.next()) {
totalValue += rs.getInt("sellingprice");
}
System.out.println"The total Value is: " + totalValue;
}catch(Exception e) {
System.out.println(e.getMessage());
}
I changed the following
rs.getInt instead of rs.getString , you can also use getDouble depending on the data you are expecting.
declare and initialize the int variable before the loop and increment it within the loop.
print the total after the loop has finished.

try {
Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost/customerinfo", "root", "");
Statement st = con.createStatement();
ResultSet rs;
String mysqlQuery = "SELECT `sellingprice` FROM cust_info";
rs =st.executeQuery(mysqlQuery);
while(rs.next()) {
String total = rs.getString("sellingprice"); // getting all the selling prices
//converting to integer
int totalValue = Integer.parseInt(total);//<----- YOUR PROBLEM
// what logic should goes here....
System.out.println(totalValue);
}
}catch(Exception e) {
System.out.println(e.getMessage());
}
You can't create your totalValue in your while statement. Each time the code cycles through the while statement, you're going to reset the total value to the latest total you got from your resultset. You want something like:
try {
Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost/customerinfo", "root", "");
Statement st = con.createStatement();
ResultSet rs;
String mysqlQuery = "SELECT `sellingprice` FROM cust_info";
rs =st.executeQuery(mysqlQuery);
int totalValue = 0; //<-- Create your total value outside of the while statement.
while(rs.next()) {
String total = rs.getString("sellingprice");
totalValue += Integer.parseInt(total);//<-- Add the selling price from the current row to the total.
System.out.println(totalValue); //<--This will print the latest total for each row in your result set
}
System.out.println(totalValue); //<-- This will print only the final total
}catch(Exception e) {
System.out.println(e.getMessage());
}
}

Try this solution , using the SUM function :
try {
Connection con = (Connection)
DriverManager.getConnection("jdbc:mysql://localhost/customerinfo", "root", "");
Statement st = con.createStatement();
ResultSet rs;
String mysqlQuery = "SELECT SUM(`sellingprice`) FROM cust_info";
rs =st.executeQuery(mysqlQuery);
int totalValue = 0;
if(rs.next()) {
String total = rs.getString("sellingprice");
if(total != null){
totalValue = Integer.parseInt(total);
}
System.out.println(totalValue);
}
}catch(Exception e) {
System.out.println(e.getMessage());
}

Can not execute Query on Mouse Event

I have following code,
private void trans_tabMouseClicked(java.awt.event.MouseEvent evt) {
try{
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/online_store","poornima","mit1234");
if(con != null){
String query = "SELECT * FROM bill";
rs = stmt.executeQuery(query);
System.out.println("fffgg");
ResultSetMetaData rsmt = rs.getMetaData();
int c = rsmt.getColumnCount();
Vector row = new Vector();
DefaultTableModel model = (DefaultTableModel)expense_table.getModel();
while(rs.next())
{
row = new Vector(c);
for(int i = 1; i <= c; i++)
{
row.add(rs.getString(i));
}
model.addRow( row );
}
}
}catch(Exception ex){
System.out.println(ex);
}
}
in the above code query is not executed. Fired null pointer exception at rs = stmt.executeQuery(query); line. I tried hours, but I can't figure out where the issue is. Please help.

because stmt is null.
use this
String query = "SELECT * FROM bill";
stmt = con.createStatement();
rs = stmt.executeQuery(query);
instead of this
String query = "SELECT * FROM bill";
rs = stmt.executeQuery(query);
refer this

how to check database table is empty or not

i have a database with a table 'admin'.But presently just creating table not having any values.table columns are user_name and password.My motive is to check whether the table is empty or not.I am using mysql database.I tried following code and its fails.Please help me.
public void nullCheck() {
PreparedStatement stmt = null;
ResultSet rs = null;
String qry = "SELECT * From admin ";
try {
stmt = (PreparedStatement) conn.prepareStatement(qry);
rs = stmt.executeQuery();
boolean empty = true;
while( rs.next() ) {
// ResultSet processing here
empty = false;
}
if( empty ) {
Util.showWarningMessageDialog("null");
}
} catch (SQLException ex) {
Logger.getLogger(RemoveFaculty.class.getName()).log(Level.SEVERE, null, ex);
}
}

If you just need to check the table then you should use query:
String qry = "SELECT count(*) From admin ";
for better performance.
And get the row count from ResultSet to check the table is null or not.
int count=0;
while( rs.next() )
{
count=rs.getInt("count");
}

Try this code, I think this will do it. I updated it coz the first I post here is not working at all, my bad.
public void nullCheck() {
PreparedStatement stmt = null;
ResultSet rs = null;
String qry = "SELECT * From admin ";
try {
stmt = (PreparedStatement) conn.prepareStatement(qry);
rs = stmt.executeQuery();
int count = 0;
while(rs.next()){
count++;
}
if(count == 0){ // if equal to 0 then the table is null
bla bla bla
}
} catch (SQLException ex) {
Logger.getLogger(RemoveFaculty.class.getName()).log(Level.SEVERE, null, ex);
}
}

Correct way to find rowcount in Java JDBC

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).

Retrieve column names from java.sql.ResultSet

With java.sql.ResultSet is there a way to get a column's name as a String by using the column's index? I had a look through the API doc but I can't find anything.

You can get this info from the ResultSet metadata. See ResultSetMetaData
e.g.
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
String name = rsmd.getColumnName(1);
and you can get the column name from there. If you do
select x as y from table
then rsmd.getColumnLabel() will get you the retrieved label name too.

In addition to the above answers, if you're working with a dynamic query and you want the column names but do not know how many columns there are, you can use the ResultSetMetaData object to get the number of columns first and then cycle through them.
Amending Brian's code:
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int columnCount = rsmd.getColumnCount();
// The column count starts from 1
for (int i = 1; i <= columnCount; i++ ) {
String name = rsmd.getColumnName(i);
// Do stuff with name
}

You can use the the ResultSetMetaData (http://java.sun.com/javase/6/docs/api/java/sql/ResultSetMetaData.html) object for that, like this:
ResultSet rs = stmt.executeQuery("SELECT * FROM table");
ResultSetMetaData rsmd = rs.getMetaData();
String firstColumnName = rsmd.getColumnName(1);

This question is old and so are the correct previous answers. But what I was looking for when I found this topic was something like this solution. Hopefully it helps someone.
// Loading required libraries
import java.util.*;
import java.sql.*;
public class MySQLExample {
public void run(String sql) {
// JDBC driver name and database URL
String JDBC_DRIVER = "com.mysql.jdbc.Driver";
String DB_URL = "jdbc:mysql://localhost/demo";
// Database credentials
String USER = "someuser"; // Fake of course.
String PASS = "somepass"; // This too!
Statement stmt = null;
ResultSet rs = null;
Connection conn = null;
Vector<String> columnNames = new Vector<String>();
try {
// Register JDBC driver
Class.forName(JDBC_DRIVER);
// Open a connection
conn = DriverManager.getConnection(DB_URL, USER, PASS);
// Execute SQL query
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
if (rs != null) {
ResultSetMetaData columns = rs.getMetaData();
int i = 0;
while (i < columns.getColumnCount()) {
i++;
System.out.print(columns.getColumnName(i) + "\t");
columnNames.add(columns.getColumnName(i));
}
System.out.print("\n");
while (rs.next()) {
for (i = 0; i < columnNames.size(); i++) {
System.out.print(rs.getString(columnNames.get(i))
+ "\t");
}
System.out.print("\n");
}
}
} catch (Exception e) {
System.out.println("Exception: " + e.toString());
}
finally {
try {
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (conn != null) {
conn.close();
}
} catch (Exception mysqlEx) {
System.out.println(mysqlEx.toString());
}
}
}
}

SQLite 3
Using getMetaData();
DatabaseMetaData md = conn.getMetaData();
ResultSet rset = md.getColumns(null, null, "your_table_name", null);
System.out.println("your_table_name");
while (rset.next())
{
System.out.println("\t" + rset.getString(4));
}
EDIT: This works with PostgreSQL as well

import java.sql.*;
public class JdbcGetColumnNames {
public static void main(String args[]) {
Connection con = null;
Statement st = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/komal", "root", "root");
st = con.createStatement();
String sql = "select * from person";
rs = st.executeQuery(sql);
ResultSetMetaData metaData = rs.getMetaData();
int rowCount = metaData.getColumnCount();
System.out.println("Table Name : " + metaData.getTableName(2));
System.out.println("Field \tDataType");
for (int i = 0; i < rowCount; i++) {
System.out.print(metaData.getColumnName(i + 1) + " \t");
System.out.println(metaData.getColumnTypeName(i + 1));
}
} catch (Exception e) {
System.out.println(e);
}
}
}
Table Name : person
Field DataType
id VARCHAR
cname VARCHAR
dob DATE

while (rs.next()) {
for (int j = 1; j < columncount; j++) {
System.out.println( rsd.getColumnName(j) + "::" + rs.getString(j));
}
}

When you need the column names, but do not want to grab entries:
PreparedStatement stmt = connection.prepareStatement("SHOW COLUMNS FROM `yourTable`");
ResultSet set = stmt.executeQuery();
//store all of the columns names
List<String> names = new ArrayList<>();
while (set.next()) { names.add(set.getString("Field")); }
NOTE: Only works with MySQL

The SQL statements that read data from a database query return the data in a result set. The SELECT statement is the standard way to select rows from a database and view them in a result set. The **java.sql.ResultSet** interface represents the result set of a database query.
Get methods: used to view the data in the columns of the current row
being pointed to by the cursor.
Using MetaData of a result set to fetch the exact column count
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int numberOfColumns = rsmd.getColumnCount();
boolean b = rsmd.isSearchable(1);
http://docs.oracle.com/javase/7/docs/api/java/sql/ResultSetMetaData.html
and further more to bind it to data model table
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Connected database successfully...");
//STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
String sql = "SELECT id, first, last, age FROM Registration";
ResultSet rs = stmt.executeQuery(sql);
//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
rs.close();
} catch(SQLException se) {
//Handle errors for JDBC
se.printStackTrace();
} catch(Exception e) {
//Handle errors for Class.forName
e.printStackTrace();
} finally {
//finally block used to close resources
try {
if(stmt!=null)
conn.close();
} catch(SQLException se) {
} // do nothing
try {
if(conn!=null)
conn.close();
} catch(SQLException se) {
se.printStackTrace();
} //end finally try
}//end try
System.out.println("Goodbye!");
}//end main
//end JDBCExample
very nice tutorial here : http://www.tutorialspoint.com/jdbc/
ResultSetMetaData meta = resultset.getMetaData(); // for a valid resultset object after executing query
Integer columncount = meta.getColumnCount();
int count = 1 ; // start counting from 1 always
String[] columnNames = null;
while(columncount <=count) {
columnNames [i] = meta.getColumnName(i);
}
System.out.println (columnNames.size() ); //see the list and bind it to TableModel object. the to your jtbale.setModel(your_table_model);

#Cyntech is right.
Incase your table is empty and you still need to get table column names you can get your column as type Vector,see the following:
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int columnCount = rsmd.getColumnCount();
Vector<Vector<String>>tableVector = new Vector<Vector<String>>();
boolean isTableEmpty = true;
int col = 0;
while(rs.next())
{
isTableEmpty = false; //set to false since rs.next has data: this means the table is not empty
if(col != columnCount)
{
for(int x = 1;x <= columnCount;x++){
Vector<String> tFields = new Vector<String>();
tFields.add(rsmd.getColumnName(x).toString());
tableVector.add(tFields);
}
col = columnCount;
}
}
//if table is empty then get column names only
if(isTableEmpty){
for(int x=1;x<=colCount;x++){
Vector<String> tFields = new Vector<String>();
tFields.add(rsmd.getColumnName(x).toString());
tableVector.add(tFields);
}
}
rs.close();
stmt.close();
return tableVector;

ResultSet rsTst = hiSession.connection().prepareStatement(queryStr).executeQuery();
ResultSetMetaData meta = rsTst.getMetaData();
int columnCount = meta.getColumnCount();
// The column count starts from 1
String nameValuePair = "";
while (rsTst.next()) {
for (int i = 1; i < columnCount + 1; i++ ) {
String name = meta.getColumnName(i);
// Do stuff with name
String value = rsTst.getString(i); //.getObject(1);
nameValuePair = nameValuePair + name + "=" +value + ",";
//nameValuePair = nameValuePair + ", ";
}
nameValuePair = nameValuePair+"||" + "\t";
}

If you want to use spring jdbctemplate and don't want to deal with connection staff, you can use following:
jdbcTemplate.query("select * from books", new RowCallbackHandler() {
public void processRow(ResultSet resultSet) throws SQLException {
ResultSetMetaData rsmd = resultSet.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); i++ ) {
String name = rsmd.getColumnName(i);
// Do stuff with name
}
}
});

U can get column name and value from resultSet.getMetaData();
This code work for me:
Connection conn = null;
PreparedStatement preparedStatement = null;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
conn = MySQLJDBCUtil.getConnection();
preparedStatement = conn.prepareStatement(sql);
if (params != null) {
for (int i = 0; i < params.size(); i++) {
preparedStatement.setObject(i + 1, params.get(i).getSqlValue());
}
ResultSet resultSet = preparedStatement.executeQuery();
ResultSetMetaData md = resultSet.getMetaData();
while (resultSet.next()) {
int counter = md.getColumnCount();
String colName[] = new String[counter];
Map<String, Object> field = new HashMap<>();
for (int loop = 1; loop <= counter; loop++) {
int index = loop - 1;
colName[index] = md.getColumnLabel(loop);
field.put(colName[index], resultSet.getObject(colName[index]));
}
rows.add(field);
}
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (preparedStatement != null) {
try {
preparedStatement.close();
}catch (Exception e1) {
e1.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
return rows;

I know, this question is already answered but probably somebody like me needs to access a column name from DatabaseMetaData by label instead of index:
ResultSet resultSet = null;
DatabaseMetaData metaData = null;
try {
metaData = connection.getMetaData();
resultSet = metaData.getColumns(null, null, tableName, null);
while (resultSet.next()){
String name = resultSet.getString("COLUMN_NAME");
}
}

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Get max value sql in Java - java

ResultSet rs = stmt.executeQuery("select MAX(GiaSP) as maxGiaSP from tbsanpham where manhom = '"+manhom+"'"); if (rs.next()) { int w = rs.getInt("maxGiaSP "); // just return this int }

Related

How to get all the prices from a particular column add them and print them

Can not execute Query on Mouse Event

how to check database table is empty or not

Correct way to find rowcount in Java JDBC

Retrieve column names from java.sql.ResultSet

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