I am trying to update a table using Java JDBC. The method I am using does not throw any errors but the table is not updating. The create table method is below:
public static void Table()
{
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.sqlite.JDBC");
c = DriverManager.getConnection("jdbc:sqlite:WalkerTechCars.db");
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "CREATE TABLE IF NOT EXISTS CUSTOMERS2 " +
"(PHONE TEXT PRIMARY KEY NOT NULL," +
" SURNAME TEXT NOT NULL, " +
" FIRSTNAME TEXT NOT NULL, " +
" HOME TEXT, " +
" ADDRESS TEXT, " +
" POSTCODE Text)";
stmt.executeUpdate(sql);
stmt.close();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
System.exit(0);
}
System.out.println("Customers2 created successfully");
}
The update method is below:
public static void updateCustomers()
{
Connection c = null;
PreparedStatement pstmt = null;
try {
Class.forName("org.sqlite.JDBC");
c = DriverManager.getConnection("jdbc:sqlite:WalkerTechCars.db");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
String query = "UPDATE CUSTOMERS2 set ADDRESS = ? where PHONE = ? ";
pstmt = c.prepareStatement(query); // create a statement
pstmt.setString(1, "1"); // set input parameter 1
pstmt.setString(2, "DOES THIS WORK"); // set input parameter 2
pstmt.executeUpdate(); // execute update statement
pstmt.close();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
System.exit(0);
}
System.out.println("Update Completed successfully HELLO");
}
I have tried to find some clear instructions on this but cant find any. I do not really understand JDBC and prepared statement very well
When autoCommit is false (c.setAutoCommit(false);), you must manually commit the transaction...
Add...
c.commit()
After pstmt.executeUpdate();
You code also has a flaw, in that if some kind of error occurs during the preparation or execution of the statement, both the Connection and PreparedStatement could be left open, causing a resource leak
If you're using Java 7+ you can use the try-with-resources feature, for example...
try {
Class.forName("org.sqlite.JDBC");
try (Connection c = DriverManager.getConnection("jdbc:sqlite:WalkerTechCars.db")) {
c.setAutoCommit(false);
System.out.println("Opened database successfully");
String query = "UPDATE CUSTOMERS2 set ADDRESS = ? where PHONE = ? ";
try (PreparedStatement pstmt = c.prepareStatement(query)) {
pstmt.setString(1, "1"); // set input parameter 1
pstmt.setString(2, "DOES THIS WORK"); // set input parameter 2
pstmt.executeUpdate(); // execute update statement
c.commit();
}
} catch (SQLException exp) {
exp.printStackTrace();
}
} catch (ClassNotFoundException exp) {
exp.printStackTrace();
System.out.println("Failed to load driver");
}
This will ensure that regardless of how you leave the try block the resource will be closed.
You might also consider taking a look at the JDBC(TM) Database Access
Your update method will set ADDRESS to 1 if there is any row in table with PHONE = does this work.
Try to put Address in 1st Input parameter and Phone 2nd Input parameter
When a connection is created, it is in auto-commit mode.
We need to use [setAutoCommit] method only when we need to make Auto Commit false and make it manual commit after executing the query.
More details at Oracle site on JDBC Transaction.
Related
I created the following class in java to make using SQLite easier when I code.
import java.sql.*;
public class Dbm {
//We want to use the connection througout the whole class so it is
//provided as a class level private variable
private Connection c = null;
//This constructor openes or creates the database provided by the arguement
//NameOfDatabase
public Dbm(String NameOfDatabase){
try {
//Database is checked for in project folder, if doesnt exist then creates database
c = DriverManager.getConnection("jdbc:sqlite:" + NameOfDatabase);
} catch ( Exception e ) {
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
System.exit(0);
}
System.out.println("Opened database successfully");
}
public void CloseDB(){
try{
c.close();
System.out.println("Closed Database Successfull");
}
catch (Exception e){
System.out.println("Failed to close Database due to error: " + e.getMessage());
}
}
public void ExecuteNoReturnQuery(String SqlCommand){
//creates a statment to execute the query
try{
Statement stmt = null;
stmt = c.createStatement();
stmt.executeUpdate(SqlCommand);
stmt.close();
System.out.println("Sql query executed successfull");
} catch (Exception e){
System.out.println("Failed to execute query due to error: " + e.getMessage());
}
}
// this method returns a ResultSet for a query which can be iterated throughd
public ResultSet ExecuteSqlQueryWithReturn(String SqlCommand){
try{
Statement stmt = null;
stmt = c.createStatement();
ResultSet rs = stmt.executeQuery(SqlCommand);
return rs;
}catch (Exception e){
System.out.println("An Error has ocured while executing this query" + e.getMessage());
}
return null;
}
}
Here is the main code in the program
import java.sql.*;
public class InstaText {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
Dbm db = new Dbm("people.db");
ResultSet rs = db.ExecuteSqlQueryWithReturn("select * from people;");
try{
String name = "";
int age = 0;
String address = "";
while (rs.isLast() == false){
name = rs.getString("name");
age = rs.getInt("age");
address = rs.getString("address");
System.out.println("Name is " + name +" age is " + age + " Address is " + address);
rs.next();
}
}catch (Exception e ){
System.out.println("Error: " + e.getMessage());
}
db.CloseDB();
}
}
But when I execute it I get the following output:
Opened database successfully
Error: function not yet implemented for SQLite
Closed Database Successfull
So how do I solve the Error "Error: function not yet implemented for SQLite"?
I am running the NetBeans Ide with the latest JDBC on mac os sierra.
Edit: Here is the output after adding e.printstacktrace(); in the catch block:
Opened database successfully
Error: function not yet implemented for SQLite
java.sql.SQLException: function not yet implemented for SQLite
Closed Database Successfull
at org.sqlite.jdbc3.JDBC3ResultSet.isLast(JDBC3ResultSet.java:155)
at instatext.InstaText.main(InstaText.java:24)
The problem is not your select query but the isLast() method you are using on the ResultSet instance to retrieve the result. Try the next() method, it should work :
while (rs.next()){
name = rs.getString("name");
age = rs.getInt("age");
address = rs.getString("address");
System.out.println("Name is " + name +" age is " + age + " Address is " + address);
rs.next();
}
You can read here :
https://github.com/bonitasoft/bonita-connector-database/issues/1
that with SQLLite, you may have some limitations with the isLast() method :
According to JDBC documentation
(http://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html)
calls to isLast() and first() methods are forbidden if the result set
type is TYPE_FORWARD_ONLY (e.g SQLite).
I'm currently using Java and JDBC to work with SQLite. When inserting a new object into a database, how am I supposed to know which id to use or how to generate it?
Here's my code I'm using:
private void insertIntoTable() {
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.sqlite.JDBC");
c = DriverManager.getConnection("jdbc:sqlite:src/test.db");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" +
"VALUES (2 , 'Brian Brianson', 32, 'California', 60000.00);";
stmt.executeUpdate(sql);
stmt.close();
c.commit();
c.close();
} catch (Exception e) {
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
}
When I'm inserting new items, how should I find out which id I should be using to insert into the database?
INTEGER PRIMARY KEY columns automatically behave as auto increment columns, q.v. the documentation. You need only insert NULL values for the ID column and SQLite will populate the value for you. That is, use this code:
String sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" +
"VALUES (null, 'Brian Brianson', 32, 'California', 60000.00);";
stmt.executeUpdate(sql);
I am trying to select data from a table using prepared statement. But it seems like I am getting syntax error which I cannot solve alone.
try {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/mydb";
String dbusername = "root";
String dbpassword = ""; // Change it to your Password
// Setup the connection with the DB
connection = DriverManager.getConnection(url, dbusername,
dbpassword);
String query = "SELECT * FROM admin WHERE username = ? AND password = ?";
try {
// connection.setAutoCommit(false);
selectUser = connection.prepareStatement(query);
selectUser.setString(1, username);
selectUser.setString(2, password);
// Execute preparedstatement
ResultSet rs = selectUser.executeQuery(query);
// Output user details and query
System.out.println("Your user name is " + username);
System.out.println("Your password is " + password);
System.out.println("Query: " + query);
boolean more = rs.next();
// if user does not exist set the validity variable to true
if (!more) {
System.out
.println("Sorry, you are not a registered user! Please sign up first!");
user.setValid(false);
}
// if user exists set the validity variable to true
else if (more) {
String name = rs.getString("name");
System.out.println("Welcome " + name);
user.setName(name);
user.setValid(true);
}
} catch (Exception e) {
System.out.println("Prepared Statement Error! " + e);
}
} catch (Exception e) {
System.out.println("Log in failed: An exception has occured! " + e);
} finally {
}
if (connection != null) {
try {
connection.close();
} catch (Exception e) {
System.out.println("Connection closing exception occured! ");
}
connection = null;
}
return user;
}
I get following error.
Prepared Statement Error! com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '? AND password = ?' at line 1
But I don't see any error in that code line.
Change
ResultSet rs = selectUser.executeQuery(query);
to
ResultSet rs = selectUser.executeQuery();
when you already prepared the statement in connection.prepareStatement(query); then why to pass the query again in selectUser.executeQuery(query);
what you want to do is use this method
ResultSet rs = selectUser.executeQuery();
You have already loaded your query inside the prepared statement here ,
selectUser = connection.prepareStatement(query);
so execute it by ,
ResultSet rs = selectUser.executeQuery();
Also read ,
How does PreparedStatement.executeQuery work?
I have problem with my SQL request, when I run my request, I receive this message error:
org.postgresql.util.PSQLException: A result was returned when none was expected.
Here is my request:
Connexion con = new Connexion();
try {
c = con.Connect();
stmt = c.createStatement();
int sqlCalcul = stmt.executeUpdate(
"SELECT inventaire FROM calcul WHERE designation='" + designation +
"' AND date=(SELECT MAX(date) FROM calcul)");
stmt.close();
// c.commit();
c.close();
} catch (Exception e) {
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
System.out.println("Records created successfully");
You should use executeQuery instead of executeUpdate:
ResultSet sqlCalcul = stmt.executeQuery("SELECT inventaire...")
executeUpdate is used for a INSERT, UPDATE, or DELETE statement, and will throw an exception if a ResultSet is returned. executeQuery should be used for SELECT statements.
Take a look at PostgreSQL's tutorial using the JDBC driver for more information.
I have a Postgresql database and I want to truncate some tables using JDBC. How do I do that?
This is what I tried, but none worked... without even any error being reported:
Using CallableStatement.
try (Connection connection = getConnection();
CallableStatement statement = connection.prepareCall("TRUNCATE " + tableName)) {
return statement.execute();
}
Using Statement.
try (Connection connection = getConnection();
Statement statement = connection.createStatement()) {
return statement.execute("TRUNCATE " + tableName);
}
Using PreparedStatement.
try (Connection connection = getConnection();
PreparedStatement statement = connection.prepareStatement("TRUNCATE " + tableName)) {
return statement.execute();
}
After the truncate, I need to commit:
try (Connection connection = getConnection();
Statement statement = connection.createStatement()) {
int result = statement.executeUpdate("TRUNCATE " + tableName);
connection.commit();
return result;
}
From the documentation:
TRUNCATE is transaction-safe with respect to the data in the tables: the truncation will be safely rolled back if the surrounding transaction does not commit.
You may run into issues if the table has dependencies. If so, truncate the parent tables first, and also use the CASCADE option.
Connection connection = getConnection();
try {
PreparedStatement statement = connection.prepareStatement("TRUNCATE " + parentTable1, parentTable2, ... + " CASCADE");
try {
return statement.execute();
} finally {
statement.close();
}
} finally {
connection.close();
}
First, if you are truncating a table, you probably want to also RESTART IDENTITY (in addition to possibly doing CASCADE, as John Hogan mentioned).
Second, as far as doing a connection.commit(), the assumption is that you have autocommit set to OFF. My Postgres was set up with it set to ON (apparently, that is sometimes the default).
If it is set to ON, then calling the commit is unnecessary, and will result in the error:
"org.postgresql.util.PSQLException: Cannot commit when autoCommit is enabled."
Third, you may not have permission to truncate a table (or restart identity). In that case, you will need to:
DELETE from your_table
SELECT setval('your_table_id', 1)
The following worked for me:
public String truncateTable(String tableName, boolean cascadeFlag) {
String message = "";
try {
connection = DriverManager.getConnection(url, username, password);
Statement statement = connection.createStatement();
String truncation = "TRUNCATE TABLE yourSchema." + tableName + " RESTART IDENTITY" + (cascadeFlag ? " CASCADE" : "");
System.out.println("truncateTable: Executing query '" + truncation + "'.");
int result = statement.executeUpdate(truncation);
// connection.commit(); // If autocommit is enabled (which it is for our DB), then throws exception after truncating the table.
statement.close();
connection.close();
} catch (SQLException sqlex) {
message = "Could not truncate table " + tableName + ". " + sqlex.getMessage();
System.err.println(message);
sqlex.printStackTrace();
}
return message;
}
Also:
public int deleteResetTable(String tableName, String fieldName) {
int affectedRows = 0;
try {
connection = DriverManager.getConnection(url, username, password);
String sql = "DELETE FROM yourSchema." + tableName;
PreparedStatement preparedStatement = connection.prepareStatement(sql);
affectedRows = preparedStatement.executeUpdate();
System.out.println("Deleted " + affectedRows+ " rows from table " + tableName + ".");
sql = "SELECT setval('yourSchema." + fieldName + "', 1)";
preparedStatement = connection.prepareStatement(sql);
affectedRows = preparedStatement.executeUpdate();
System.out.println("Reset " + affectedRows+ " values from table " + tableName + ".");
} catch (SQLException ex) {
System.out.println("Failed to delete rows from " + tableName + " " + ex.getMessage());
}
return affectedRows;
}