Develop Reference

Get max value sql in 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
}

Passing array parameter in prepare statement - getting "java.sql.SQLFeatureNotSupportedException"

I am facing error java.sql.SQLFeatureNotSupportedException in my prepare statement. I am using Mysql database.
Below is my code.
class tmp {
public static void main(String arg[]) {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(
"jdbc:mysql://localhost/sample", "root", "root");
PreparedStatement pst = conn
.prepareStatement("select * from userinfo where firstname in(?)");
String[] Parameter = { "user1", "Administrator" };
Array sqlArray = conn.createArrayOf("VARCHAR", Parameter);
pst.setArray(1, sqlArray);
ResultSet rs = pst.executeQuery();
while (rs.next()) {
System.out.println(rs.getInt(1));
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

For Mysql -
Setting array is not possible in Mysql.
Instead of that you can form a query for (?,?,..) in the loop and same way for setting values.
String[] Parameter = { "user1", "Administrator" };
String query = "select * from userinfo where firstname in (";
String temp = "";
for(i = 0; i < Parameter.length; i++) {
temp += ",?";
}
temp = temp.replaceFirst(",", "");
temp += ")";
query = query + temp;
PreparedStatement pst = conn.prepareStatement(query);
so query becomes
select * from userinfo where firstname in (?,?)
and pass values also using loop.
For Oracle -
ArrayDescriptor arrayDescriptor = ArrayDescriptor.createDescriptor("CHAR_ARRAY", conn);
String[] Parameter = { "user1", "Administrator" };
java.sql.Array sqlArray = new oracle.sql.ARRAY(arrayDescriptor, conn, content);
.
.
pstmt.setArray(1, sqlArray);

Error message is very clear. And MySQL does not support custom data types.
Currently MySQL is supporting only:
Numeric Type
Date and Time Type
String Type
Or, you can use each of the input values as a set of values of IN function in MySQL.
Change your JAVA code as follows:
StringBuilder sbSql = new StringBuilder( 1024 );
sbSql.append( "select * from userinfo where firstname in(" );
for( int i=0; i < Parameter.length; i++ ) {
if( i > 0 ) sbSql.append( "," );
sbSql.append( " ?" );
} // for
sbSql.append( " )" );
PreparedStatement pst = conn.prepareStatement( sbSql.toString() );
for( int i=0; i < Parameter.length; i++ ) {
pst.setString( i+1, Parameter[ i ] );
} // for
ResultSet rs = pst.executeQuery();

Convert List to a comma separated String and use it.
Class Tmp {
public static void main(String arg[]) {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(
"jdbc:mysql://localhost/sample", "root", "root");
// Consider this list is already constructed
List<String> parameter = new ArrayList<String>();
parameter.add("user1");
parameter.add("Administrator");
String parameterStr = "'" + String.join("','", parameter) + "'";
PreparedStatement pst = conn.prepareStatement("select * from userinfo where firstname in(" + parameterStr + ")");
ResultSet rs = pst.executeQuery();
while (rs.next()) {
System.out.println(rs.getInt(1));
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

Inserting records into a MySQL table using Java

I created a database with one table in MySQL:
CREATE DATABASE iac_enrollment_system;
USE iac_enrollment_system;
CREATE TABLE course(
course_code CHAR(7),
course_desc VARCHAR(255) NOT NULL,
course_chair VARCHAR(255),
PRIMARY KEY(course_code)
);
I tried to insert a record using Java:
// STEP 1: Import required packages
import java.sql.*;
import java.util.*;
public class SQLInsert {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost:3306/iac_enrollment_system";
// Database credentials
static final String USER = "root";
static final String PASS = "1234";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
Scanner scn = new Scanner(System.in);
String course_code = null, course_desc = null, course_chair = null;
try {
// STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
// STEP 3: Open a connection
System.out.print("\nConnecting to database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println(" SUCCESS!\n");
// STEP 4: Ask for user input
System.out.print("Enter course code: ");
course_code = scn.nextLine();
System.out.print("Enter course description: ");
course_desc = scn.nextLine();
System.out.print("Enter course chair: ");
course_chair = scn.nextLine();
// STEP 5: Excute query
System.out.print("\nInserting records into table...");
stmt = conn.createStatement();
String sql = "INSERT INTO course " +
"VALUES (course_code, course_desc, course_chair)";
stmt.executeUpdate(sql);
System.out.println(" SUCCESS!\n");
} catch(SQLException se) {
se.printStackTrace();
} catch(Exception e) {
e.printStackTrace();
} finally {
try {
if(stmt != null)
conn.close();
} catch(SQLException se) {
}
try {
if(conn != null)
conn.close();
} catch(SQLException se) {
se.printStackTrace();
}
}
System.out.println("Thank you for your patronage!");
}
}
The output appears to return successfully:
But when I select from MySQL, the inserted record is blank:
Why is it inserting a blank record?

no that cannot work(not with real data):
String sql = "INSERT INTO course " +
"VALUES (course_code, course_desc, course_chair)";
stmt.executeUpdate(sql);
change it to:
String sql = "INSERT INTO course (course_code, course_desc, course_chair)" +
"VALUES (?, ?, ?)";
Create a PreparedStatment with that sql and insert the values with index:
PreparedStatement preparedStatement = conn.prepareStatement(sql);
preparedStatement.setString(1, "Test");
preparedStatement.setString(2, "Test2");
preparedStatement.setString(3, "Test3");
preparedStatement.executeUpdate();

this can also be done like this if you don't want to use prepared statements.
String sql = "INSERT INTO course(course_code,course_desc,course_chair)"+"VALUES('"+course_code+"','"+course_desc+"','"+course_chair+"');"
Why it didnt insert value is because you were not providing values, but you were providing names of variables that you have used.

This should work for any table, instead of hard-coding the columns.
//Source details
String sourceUrl = "jdbc:oracle:thin:#//server:1521/db";
String sourceUserName = "src";
String sourcePassword = "***";
// Destination details
String destinationUserName = "dest";
String destinationPassword = "***";
String destinationUrl = "jdbc:mysql://server:3306/db";
Connection srcConnection = getSourceConnection(sourceUrl, sourceUserName, sourcePassword);
Connection destConnection = getDestinationConnection(destinationUrl, destinationUserName, destinationPassword);
PreparedStatement sourceStatement = srcConnection.prepareStatement("SELECT * FROM src_table ");
ResultSet rs = sourceStatement.executeQuery();
rs.setFetchSize(1000); // not needed
ResultSetMetaData meta = rs.getMetaData();
List<String> columns = new ArrayList<>();
for (int i = 1; i <= meta.getColumnCount(); i++)
columns.add(meta.getColumnName(i));
try (PreparedStatement destStatement = destConnection.prepareStatement(
"INSERT INTO dest_table ("
+ columns.stream().collect(Collectors.joining(", "))
+ ") VALUES ("
+ columns.stream().map(c -> "?").collect(Collectors.joining(", "))
+ ")"
)
)
{
int count = 0;
while (rs.next()) {
for (int i = 1; i <= meta.getColumnCount(); i++) {
destStatement.setObject(i, rs.getObject(i));
}
destStatement.addBatch();
count++;
}
destStatement.executeBatch(); // you will see all the rows in dest once this statement is executed
System.out.println("done " + count);
}

There is a mistake in your insert statement chage it to below and try :
String sql = "insert into table_name values ('" + Col1 +"','" + Col2 + "','" + Col3 + "')";

Result set returns 3 rows but i am only able to print 2?

The code below gets the information i require from my database but is not printing out all of the information. Firstly i know it is getting all of the correct information from the table because i have tried the query in sql developer.
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
conn = getConnection();
String query = "SELECT menu.menu_id, menu_title, dish.dish_id, dish_name, dish_description, dish_price, menu.week_no "
+ "FROM menu, dish, menu_allocation "
+ "WHERE menu.active = '1' "
+ "AND menu.menu_id = menu_allocation.menu_id "
+ "AND dish.dish_id = menu_allocation.dish_id "
+ "AND menu.week_no IN (09, 10, 11)";
stmt = conn.createStatement();
rs = stmt.executeQuery(query);
MenuList list = null;
while (rs.next()) {
list = new MenuList(rs);
System.out.println(rs.getRow());
}
for (int pos = 0; pos < list.size(); pos++) {
Menu menu = list.getMenuAt(pos);
System.out.println(menu.getDescription());
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
rs.close();
stmt.close();
conn.close();
} catch (SQLException e) {
}
}
}
The output from the terminal is as follows:
3 //Number of rows
Fish and Chips //3rd row
Chocolate Cake //2nd row
//Here should be 1st row
BUILD SUCCESSFUL (total time: 2 seconds)
Even though it says there are three rows it has only printed the two. Can anybody see if there is a problem with the above?

It's hard to be sure without seeing the code for the MenuList class but I don't think you need to loop over the ResultSet as MenuList does that for you.
As the MenuList constructor takes the ResultSet in rs as a parameter it probably loops over the ResultSet to create its entries. As you've already called rs.next() in the while of your loop the MenuList misses the first result.
I think you should replace all this:
MenuList list = null;
while (rs.next()) {
list = new MenuList(rs);
System.out.println(rs.getRow());
}
With:
MenuList list = new MenuList(rs);

I would suggest you use a debugger so you understand what your progam is doing.
You appear to be only keeping the last row loaded, so while you have 3 rows, you only keep the last. It appears you are getting two values from the last row.

public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
conn = getConnection();
String query = "SELECT menu.menu_id, menu_title, dish.dish_id, dish_name, dish_description, dish_price, menu.week_no "
+ "FROM menu, dish, menu_allocation "
+ "WHERE menu.active = '1' "
+ "AND menu.menu_id = menu_allocation.menu_id "
+ "AND dish.dish_id = menu_allocation.dish_id "
+ "AND menu.week_no IN (09, 10, 11)";
stmt = conn.createStatement();
rs = stmt.executeQuery(query);
MenuList[3] list = null;
int idx = 0; //Add index
while (rs.next()) {
list[idx] = new MenuList(rs); //use index
idx++; //increment index
System.out.println(rs.getRow());
}
for (int pos = 0; pos < list.size(); pos++) {
Menu menu = list.getMenuAt(pos);//Don't know that
//get menu by index
System.out.println(menu.getDescription());
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
rs.close();
stmt.close();
conn.close();
} catch (SQLException e) {
}
}
}

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");
}
}