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Select * From java with preparedStatement [duplicate]

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Java MYSQL Prepared Statement Error: Check syntax to use near '?' at line 1
(2 answers)
Closed 1 year ago.
I faced this problem today with my select SQL. This method is supposed to show data from database in tex tfields. I changed it from statement to preparedStatement, but I faced a problem.
public Entreprise loadDataModify(String id) {
Entreprise e = new Entreprise();
PreparedStatement stmt;
try {
String sql = "SELECT * FROM user WHERE mail=?";
stmt = cnx.prepareStatement(sql);
stmt.setString(1, id);
ResultSet rst = stmt.executeQuery(sql);
while (rst.next()) {
stmt.setString(2, e.getNom());
stmt.setString(3, e.getEmail());
stmt.setString(4, e.getTel());
stmt.setString(5, e.getOffre());
}
} catch (SQLException ex) {
System.out.println(ex.getMessage());
}
return e;
}
It shows i have problem with syntax and the output is " nu

You're calling the wrong method. Unlike Statement, when you're using a PreperedStatement you should first set the values for the parameters, and after you can call on that instance executeQuery() method.
Also, it's a best practice to use try-with-resources, because a Statement or PreparedStament object is a Resource (a resource is a class that implements AutoCloseable interface) and you have to close it. Using try-with-resources, it's done automatically.
The ResultSet instance is also a resource, but it's closed when the statement object is closed, so you don't have to close it explicitly.
So, the best way to solve your problem will be:
String selectAllByMail = "SELECT * FROM user WHERE mail=?";
try (PreparedStatement prpStatement = connection.prepareStatement(selectAllByMail)) {
// use prpStatement
prpStatement.setString(1, id);
ResultSet resultSet = prpStatement.executeQuery();
while (resultSet.next()) {
// process resultSet
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}

You are not filling your Enterprise object. And you are not using executeQuery() function correctly. As seen below, the parameter inside the brackets has been removed. PreparedStatements first of all need the values of the parameters (your ? in the query) and then the formed query has to be executed. If you give a String parameter to executeQuery() then the query in the brackets will be executed.
And the part where Enterprise is being filled could be seen below.
This would be the correct way:
public Entreprise loadDataModify(String id) {
Entreprise e = new Entreprise();
PreparedStatement stmt;
try {
String sql = "SELECT * FROM user WHERE mail=?";
stmt = cnx.prepareStatement(sql);
stmt.setString(1, id);
ResultSet rst = stmt.executeQuery();
while (rst.next())
{
// rst keeps the data, so you have to traverse it and get the data from it in this way.
e.setNom( rst.getString("HERE EITHER THE COLUMN NAME OR INDEX"));
e.setEmail( rst.getString("HERE EITHER THE COLUMN NAME OR INDEX"));
e.setTel( rst.getString("HERE EITHER THE COLUMN NAME OR INDEX"));
e.setOffre( rst.getString("HERE EITHER THE COLUMN NAME OR INDEX"));
}
} catch (SQLException ex) {
System.out.println(ex.getMessage());
}
return e;
}

Your call to executeQuery() should not be passing the query string. Use this version:
String sql = "SELECT * FROM user WHERE mail=?";
stmt = cnx.prepareStatement(sql);
stmt.setString(1, id);
ResultSet rst = stmt.executeQuery();
while (rst.next()) {
// process result set
}
Your current code is actually calling some overloaded Statement#executeQuery() method, which is not the version of the method which you want to be calling.

Using Symbols with Prepared Statement parameters in JAVA

How do I used % in the parameter for the code below? it works if I just use it directly in the query without the rset.setString(). Thanks!
try (Connection con = DriverManager.getConnection(connection);
PreparedStatement prepstmt = con.prepareStatement("SELECT {fn SUBSTRING(VS_TABLE_KEY,3,18)} FROM VP_SD_TABLE WHERE {fn SUBSTRING(VS_DESCRIPT,3,62)} LIKE ?");
ResultSet rset = prepstmt.executeQuery()
) {
prepstmt.setString(1,"DI%");
while (rset.next()) {
System.out.println(rset.getString("VS_TABLE_KEY"));
}
} catch (SQLException e) {
e.printStackTrace();
System.exit(1);
}

You're executing the query before you set the parameter. You should get an exception when you run this code, not just an empty result set.

Getting MySql command result in servlet java

Basically I am trying to find how many people in mysql database are registered by a specific name using SELECT command with my java program. The command executes without any error but the result is something different than I have in my db.
Here is my java code I am using to get UIDs:
public void usernameAvail_fun(){
String query = "SELECT UID FROM db.tb WHERE UFN=\"myuid\"";
ResultSet ursa;
try {
ursa = st.executeQuery(query);
System.out.println(ursa.toString());
} catch (SQLException e) {
e.printStackTrace();
}
}
and i happen to get the result as: com.mysql.jdbc.JDBC42ResultSet#11719758

You are printing a java object so output is there. If you want to print uid use following statement -
while (ursa.next()){
System.out.println(ursa.getString(1));
}

Initialize ursa to null first.
adding a PreparedStatement
public void usernameAvail_fun(){
String query = "SELECT UID FROM db.tb WHERE UFN=\"myuid\"";
ResultSet ursa= null;
try {
PreparedStatement stmt = con.prepareStatement(query);
ursa= stmt.executeQuery();
while(ursa.next()) //print
{
ursa.getString(1); //or ursa.getString("//your column name");
}
}
catch (SQLException e) {
e.printStackTrace();
}
}

Getting all data between 2 days in MySql Java

I want to select all data from database table between given 2 specific dates and add that data to a jtable.
Below is my code to retrieve data from the database; But all the data is not shown by this code .. What is the error I done here?
private void updateTable(){
String fday = ((JTextField)day_chooser.getDateEditor().getUiComponent()).getText();
String tday = ((JTextField)day_chooser.getDateEditor().getUiComponent()).getText();
try {
String sql = "SELECT * FROM saleinfo WHERE SaleDate BETWEEN '"+fday+"' AND '"+tday+"'";
pst=conn.prepareStatement(sql);
rs=pst.executeQuery();
tbl.setModel(DbUtils.resultSetToTableModel(rs));
} catch (Exception ex) {
JOptionPane.showMessageDialog(null, "Error : "+ex);
}
}

Leverage the JDBC drive and it's ability to map between data types from Java to the database, leverage the power of the PreparedStatement
I'm using prepared statements pst is the prepare statement
BUT, you're not using it properly, see Using Prepared Statements for more details.
Start by getting the Date value from the date picker (I'm guessing here, but I assume they have some kind of getDate method) and then bind the values to the wildcard columns of the query, for example...
Date fday = day_chooser.getDate();
Date tday = day_chooser.getDate();
try {
String sql = "SELECT * FROM saleinfo WHERE SaleDate BETWEEN ? AND ?";
try (PreparedStatement pst = conn.prepareStatement(sql)) {
pst.setDate(1, new java.sql.Date(fday.getTime()));
pst.setDate(2, new java.sql.Date(tday.getTime()));
try (ResultSet rs = pst.executeQuery()) {
tbl.setModel(DbUtils.resultSetToTableModel(rs));
}
}
} catch (Exception ex) {
JOptionPane.showMessageDialog(null, "Error : " + ex);
ex.printStackTrace();
}
Don't assume anything about the format, this will just cause you no end of grieve if you ever have to change databases

refactor JDBC function

I am trying to create a simple web app that saves user data from a form to a database and reads the content of the database back to browser upon request. Following are the functions I have written so far.
connectToDB() // connects to database
addEmployee() // adds employee to database
displayEmployee() // returns a resultSet
isExisted(int staffID) // checks if the staff already exists
Database connection function:
public void connectToDB(){
try{
// load Apache derby driver
Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
} catch(ClassNotFoundException e) {
System.err.println(e);
}
try{
connection = DriverManager.getConnection(DBNAME, USERNAME, PASSWORD);
} catch(SQLException e){
System.err.println(e);
}
} // end connectToDB
Display Employee function:
public ResultSet displayEmployee(){
connectToDB();
ResultSet result = null;
try{
Statement stmt = connection.createStatement();
String query = "SELECT * FROM APP.ADDRESSBOOK";
result = stmt.executeQuery(query);
} catch(SQLException e) {
System.err.println(e);
}
return result;
}
Check if employee exists:
public boolean isExisted(int StaffID){
connectToDB();
try{
Statement stmt = connection.createStatement();
String query = "SELECT StaffNum FROM APP.ADDRESSBOOK WHERE StaffNum = " + staff_number;
ResultSet result = stmt.executeQuery(query);
while(result.next()){
int temp = result.getInt(1);
if(temp == staff_number){return true;}
}
} catch(SQLException e) {
System.err.println(e);
}
return false;
}
As you can see, if you compare the displayEmployee() and isExisted(), I am repeating mysel. Both the function works but I am looking to refactor the code. In those function I havent closed the connection. If there were 20 functions in the web app that connects to the database my code would stink.
I am looking something like this:
* THIS CODE DOESNT WORK ******
private Statement queryDB(query){
connectToDB();
Statement stmt;
try{
stmt = connection.createStatement();
} catch(SQLException e) {
System.err.println(e);
}
return stmt;
// code for closing connection
}
public ResultSet DisplayEmployee(){
String query = "SELECT * FROM APP.ADDRESSBOOK";
Statement stmt = queryDB(query);
ResultSet result = stmt.executeQuery(query);
return result;
}
Thanks.

Using raw JDBC produces a lot of unsightly boilerplate code. One solution is to use Spring JDBC Template.
In addition you will get the sql exception hierarchy which will manage the underlying JDBC exceptions automatically as runtime exceptions.
For more see:
Introduction to Spring Framework JDBC

A couple of comments:
The catch statement of ClassNotFoundException should throw an exception and shouldn't continue further.
It is not a good idea to return resultsets from a method that obtained them upon statement execution, since it is the responsibility of that method to close it. Instead, you should either read out the results into objects or cache them into CachedRowSet if your downstream functions expect a resultset.
The connectToDB method should return a successful connection or throw exception.
You could write a method that takes in an SQL query and return the results as objects so that this method can be used for retrieving based on different criteria as long you are retrieving the objects of same type.
isExisted is using staff_number which I think you intend it to be staffID. If you found a row with this value, then there is no need to check if the result set contained the row with this value, right?
My two cents!