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.

What does "java.sql.SQLException: Unsupported feature" mean?

My question is related to this post and a post of mine . I am trying to pass REF_CURSOR as an IN parameter while calling a PL/SQL procedure using JDBC. Here is my code:
public int printMaxSalAllDept()
{
Connection conn = null;
OracleCallableStatement callStmt = null;
int rowCount = -1;
try
{
// Register the Jdbc Driver
// Class.forName(JDBC_DRIVER_ORACLE);
// Create a Database connection
conn = DriverManager.getConnection(DB_URL,DB_USER,DB_PWD);
// Create a query string to get the ResultSet of your choice
String getRsQuery = "SELECT e.department_id , e.last_name , "
+ "e.salary FROM employees e , (SELECT department_id , "
+ "MAX(salary) AS maxSal FROM employees GROUP BY department_id) "
+ "m WHERE e.department_id = m.department_id "
+ "AND e.salary = m.maxSal ORDER BY e.salary";
// Create a Statement
Statement stmt = conn.createStatement();
// Execute the statement
ResultSet rs = stmt.executeQuery(getRsQuery);
// Create a SQL String
String callProc = "{ call HR.EMP_PKG.print_max_sal_all_dept(? , ?) }";
// Create a Callable Statement
callStmt = (OracleCallableStatement) conn.prepareCall(callProc);
// Bind values to the IN parameter
callStmt.setCursor(1, rs);
// callStmt.setNull(1,OracleTypes.CURSOR);
// Register OUT parameters type to the SQL type of the value returned
callStmt.registerOutParameter(2, java.sql.Types.NUMERIC);
// Execute Callable Statements
callStmt.execute();
// Retrieve value from the OUT parameters
rowCount = callStmt.getInt(0);
System.out.println("Number of rows in the cursor :" + rowCount);
}
catch (SQLException se)
{
System.out.println("Exception occured in the database");
System.out.println("Exception message: "+ se.getMessage());
System.out.println("Database error code: "+ se.getErrorCode());
se.printStackTrace();
}
finally
{
// Clean up
if(callStmt != null)
{
try
{
callStmt.close();
}
catch (SQLException se2)
{
se2.printStackTrace();
}
}
if(conn != null)
{
try
{
conn.close();
}
catch (SQLException se2)
{
se2.printStackTrace();
}
}
}
return rowCount;
}
When I run the above code I get the following exception:
Exception occured in the database
java.sql.SQLException: Unsupported feature
at oracle.jdbc.driver.OraclePreparedStatement.setCursorInternal(OraclePreparedStatement.java:5867)
at oracle.jdbc.driver.OracleCallableStatement.setCursor(OracleCallableStatement.java:5297)
at oracle.jdbc.driver.OraclePreparedStatementWrapper.setCursor(OraclePreparedStatementWrapper.java:410)
at com.rolta.HrManager.printMaxSalAllDept(HrManager.java:1038)
at com.rolta.HrManager.main(HrManager.java:1344)
Exception message: Unsupported feature
Database error code: 17023
I have seen couple of posts in this forum and others which suggests updating to the latest version of JDBC driver fixes this issue. In my case I am using the latest version of JDBC driver for Oracle ( ojdbc6.jar the very first jar under Oracle Database 11g Release 2 11.2.0.4 JDBC Drivers) . So i don't think its the version that's causing the issue.
If what I was doing was illegal the exception message thrown would have indicated that. But here with "Unsupported Feature" message it seems like this feature is either unavailable for my database(or its version that I am using (11g) ) or for the version of the JDBC driver that I am using. Is this the right interpretation of this exception ?

I would say that the feature is not supported in any version of the JDBC driver, and will never be supported. The version of the database in this situation is not relevant.
I can't say why there ever was a setCursor() method declared in OraclePreparedStatement. I would guess that it was a mistake in the design of the API. In fact, you get a deprecation warning if you compile any code that attempts to call setCursor():
C:\>javac -Xlint JavaRefCursorTest.java
JavaRefCursorTest.java:28: warning: [deprecation] setCursor(int,ResultSet) in OraclePreparedStatement has been deprecated
((OracleCallableStatement)cstmt2).setCursor(1, rSet);
^
1 warning
This deprecation warning suggests that Oracle are planning to remove this method in the future.
I've also run my JavaRefCursorTest class from my answer to one of your previous questions with the Oracle 12c JDBC driver (ojdbc7.jar). The end result is only slightly different: the type of exception thrown when calling setCursor() is java.sql.SQLFeatureNotSupportedException instead of java.sql.SQLException. So upgrading the JDBC driver JAR won't help.
In your case, I can't see the reason why you would want to get a ref cursor out of the database and into a JDBC ResultSet, only to pass the same ResultSet straight back to the database. You can call the procedure with a ref cursor directly, using a PL/SQL block such as the one below:
String plsql =
"DECLARE" +
" l_curs SYS_REFCURSOR; " +
"BEGIN" +
" OPEN l_curs FOR" +
" SELECT e.department_id , e.last_name ," +
" e.salary FROM employees e , (SELECT department_id ," +
" MAX(salary) AS maxSal FROM employees GROUP BY department_id)" +
" m WHERE e.department_id = m.department_id" +
" AND e.salary = m.maxSal ORDER BY e.salary;" +
"" +
" HR.EMP_PKG.print_max_sal_all_dept(l_curs, ?);" +
"END;"
PreparedStatement stmt = conn.prepareStatement(plsql);
stmt.registerOutParameter(1, java.sql.Types.NUMERIC);
stmt.execute();

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.

Delete all tables of Database

I have a Database named KG. I want to delete all tables in this Database using java and then create them again (purpose is to truncate ALL data. Deleting tables as per advice of someone here at stackoverflow). What i need is a single command that can delete all tables. From this link i took this command
Drop Database KG
This command is not working with my case. Is there any other way to delete all Tables?
Editted
Code I am Using is
{
dbConnect();
try {
stmt = c.createStatement();
sql = "Drop Database KG";
stmt.executeUpdate(sql);
c.commit();
stmt.close();
c.close();
System.out.println("Database Deleted!");
} catch (SQLException e) {
System.err.println("Delete Database Query: " + sql);
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
}
and
public void dbConnect() {
try {
Class.forName("org.sqlite.JDBC");
c = DriverManager.getConnection("jdbc:sqlite:KG.s3db");
c.setAutoCommit(false);
System.out.println("Connected");
} catch (ClassNotFoundException | SQLException e) {
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
}
Error i am getting is
Delete Database: Drop Database KG
java.sql.SQLException: near "Database": syntax error
Note:
I have achieved it but by writing a large number of Lines of Code. Used command
Drop Table If Exists tablename
did this in loop.

You can not drop a sqlite database. Just delete the database file and open the database again.

SQLite - executeUpdate exception not caught when database does not exist? (Java)

So I was purposely trying to break my program, and I've succeeded.
I deleted the sqlite database the program uses, while the program was running, after I already created the connection. Then I attempted to update the database as seen below.
Statement stmt;
try
{
stmt = Foo.con.createStatement();
stmt.executeUpdate("INSERT INTO "+table+" VALUES (\'" + itemToAdd + "\')");
}
catch(SQLException e)
{
System.out.println("Error: " + e.toString());
}
The problem is, it didn't catch the exception, and continued to run as if the database was updated successfully. Meanwhile the database didn't even exist at that point since this was after I deleted it.
Doesn't it check if the database still exists when updating?
Do I have to check the database connection manually, every time I update to ensure that the database wasn't corrupted/deleted?
Is this the way it is normally done, or is there a simpler/more robust approach?
Thank you.

Interestingly, I found that if I delete my database when using it and then attempt to update it, it updates the database in its new location (in the trash!). You cannot permanently delete it while it is in the trash can and you are accessing it via your program.

It looks like this is not a SQLException that is thrown...
Try catching every Exception type and see if you get your error :
Statement stmt;
try
{
stmt = Foo.con.createStatement();
stmt.executeUpdate("INSERT INTO "+table+" VALUES (\'" + itemToAdd + "\')");
}
catch(Exception e)
{
System.out.println("Error: " + e.toString());
}
or
Statement stmt;
try
{
stmt = Foo.con.createStatement();
stmt.executeUpdate("INSERT INTO "+table+" VALUES (\'" + itemToAdd + "\')");
}
catch(Throwable e)
{
System.out.println("Error: " + e.toString());
}