Develop Reference

PSQLException thrown when trying to execute SELECT query

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.

JDBC update using prepared statement

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.

SQLite Database locking up on Delete Command

I have a problem where I can't seem to get this simple delete command working. Everytime I run it it just locks the database and crashes
The id parameter exists in the database
the database is small. Only a few tables.
update commands work completely fine.
The id is an in and resulting command is - DELETE from Employees where ID = 2;
public static void EmployeeDeleteByID(int idIn){
Connection c = null;
Statement stmt = null;
try {
c = Connect();
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "DELETE from Employees where ID = " + idIn + ";";
System.out.println(sql);
stmt.executeUpdate(sql);
c.commit();
stmt.close();
c.close();
} catch ( Exception e ) {
System.err.println("Error 1 : " + e.getClass().getName() + ": " + e.getMessage() );
System.exit(0);
}
System.out.println("Operation done successfully");
}
Error after running : java.sql.SQLException: database is locked

"database is locked" means that some other connection still has an active transaction.
If there is no other process accessing the database, you have to check all connections in your program; at least one of them forgot a commit().

The code actually works fine.
It turned out another method was being called to fill a JCombo which was keeping a connection open due to an error being caused by calling a null value from database.
It wasnt obvious as there was no code in the exception box.
Silly little problem so people always make an error throw some kind of stack trace or warning.
Thanks

Unable to figure out JDBC ClassNotFoundException (JTDS driver)

So a little background on my problem: I am trying to copy over a table on an Microsoft SQL system from an Oracle database. Besides giving password and user access to the table I cannot edit or do anything to the MSSQL database.
I successfully used the Oracle SQL Developer to connect and view the tables I want (using a third party JDBC driver), but I want to set up an automated copy-over into my Oracle database so I am attempting to use the same driver in some stored java code.
I have a java function that all it should do is go and count the number of entries in the table. So far my code looks like:
public static String getCount() {
Statement stmt = null;
Connection conn = null;
int rowCount = 0;
String message = "";
try {
Class.forName("net.sourceforge.jtds.jdbc.Driver");
}
catch(ClassNotFoundException e) {
System.err.println("Error loading driver: " + e);
message = message + e + " -ER1 \n";
}
try {
conn = DriverManager.getConnection("jdbc:jtds:sqlserver://site.school.edu:2000/ACCESS", "user", "password");
stmt = conn.createStatement();
String strSelect = "select 1 as field;";
ResultSet rset = stmt.executeQuery(strSelect);
while (rset.next()) {
++rowCount;
}
}
catch(SQLException ex) {
ex.printStackTrace();
message = message + ex.getSQLState() + " -ER2";
}
finally {
try {
if (stmt != null) stmt.close();
if (conn != null) conn.close();
} catch(SQLException ex) {
ex.printStackTrace();
message = message + ex.getSQLState() + "-ER3";
}
}
return message;
}
Which is being calling from a stored function :
CREATE OR REPLACE function Schema.java_testMessage return varchar2
as language java
name 'ConnectAndQuery.getCount() return java.lang.String';
Which I am calling from a script in TOAD:
set serveroutput on;
declare
words varchar2(400);
begin
words := KSL_ADMIN.java_testMessage;
dbms_output.put_line(words);
end;
However the result is that I'm getting:
java.lang.ClassNotFoundException: net/sourceforge/jtds/jdbc/Driver -ER1
08001 -ER2
PL/SQL procedure successfully completed.
I have the jar file within the class path, I can't think of any reason it shouldn't have the nessecary permissions to see the jar, and as far as I can tell I have everything spelled correctly.
Please help me figure out what I am doing wrong. Or if there is perhaps an easier way to go about connecting an Oracle DB to an MSSQL DB without really installing anything. Any knowledge on this is welcome as I am pretty new to a lot of this.

Oracle has its own internal java virtual machine and it does not use the system classpath. If you need external libraries you must “load” them into the internal JVM. You can do this using Oracle's loadjava tool.
See the Oracle's loadjava documentation (http://docs.oracle.com/cd/B28359_01/java.111/b31225/cheleven.htm#JJDEV10060)

Connecting to MySQL using Java on Debian

I am trying to connect to MySQL database with Java and I get the following error:
SQLException: 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 '????????????????' at line 1
I cannot understand the error and searched a lot on the web but did not found anything. This is the code I am using:
try
{
Class.forName("com.mysql.jdbc.Driver").newInstance();
}
catch (Exception E)
{
System.err.println("Unable to load driver");
E.printStackTrace();
}
try
{
Connection C = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/DATABASE_NAME","USERNAME","PASSWORD");
Statement Stmt = C.createStatement();
ResultSet RS = Stmt.executeQuery("SELECT somefield FROM sometable");
while (RS.next())
{
System.out.print("\"" + RS.getString(1) + "\"");
System.out.print(" by " + RS.getString(2));
System.out.println(": " + RS.getString(3));
}
C.close();
RS.close();
Stmt.close();
}
catch (SQLException E)
{
System.out.println("SQLException: " + E.getMessage());
System.out.println("SQLState: " + E.getSQLState());
System.out.println("VendorError: " + E.getErrorCode());
}
The SQL query above is an example for the question. The one I am using works without any problem in MySQL console. In fact, even if I remove the query and the statement from the code above, I still get the same error.
Can someone help?
Thanks in advance

Most likely it's because you're using
select field from table- table is a SQL reserved word. If you want to do this query, you'll probably need to do
select field from `table`
with the word table in back ticks.