We Keep Coding

Why does H2 alias duplicate inserted rows?

I have created the following H2 alias:
CREATE ALIAS INSERT_CHANGE_RECORD AS '
java.sql.ResultSet insertChangeRecord(final java.sql.Connection conn) throws java.sql.SQLException
{
String sql = "insert into `change_records` (`made_when`, `made_by`) values (CURRENT_TIMESTAMP(9), ''admin'');";
java.sql.PreparedStatement ps = conn.prepareStatement(sql, java.sql.Statement.RETURN_GENERATED_KEYS);
ps.executeUpdate();
java.sql.ResultSet results = ps.getGeneratedKeys() ;
return results;
}
';
Weirdly enough, when I call the alias (once) using call INSERT_CHANGE_RECORD(); 3 identical records are created in the table, instead of one.
When I use the following definition of the alias instead (the difference is that I actually retrieve the generated ID from the resultset), only 1 row is inserted.
CREATE ALIAS IF NOT EXISTS INSERT_CHANGE_RECORD AS '
Long insertChangeRecord(final java.sql.Connection conn) throws java.sql.SQLException
{
String sql = "insert into `change_records` (`made_when`, `made_by`) values (CURRENT_TIMESTAMP(9), ''admin'');";
java.sql.PreparedStatement ps = conn.prepareStatement(sql, java.sql.Statement.RETURN_GENERATED_KEYS);
ps.executeUpdate();
java.sql.ResultSet results = ps.getGeneratedKeys();
results.next();
return results.getLong(1);
}
';
Is this a bug in H2, or is there any reasonable explanation for this behavior? I'm using H2 2.1.210.
Here is the DDL of the table that I insert into.
CREATE TABLE IF NOT EXISTS `change_records` (
`id` BIGINT NOT NULL AUTO_INCREMENT CONSTRAINT `change_records_id_pk` PRIMARY KEY,
`made_when` TIMESTAMP (9) WITH TIME ZONE NOT NULL,
`made_by` VARCHAR NOT NULL
);

Function aliases returning a ResultSet are called multiple times. You need to check URL of passed connection. If it is equal to jdbc:columnlist:connection, you need to return an empty ResultSet with properly configured columns, you can use org.h2.tools.SimpleResultSet or some other implementation. These invocations are performed during compilation or recompilation of the query before its actual execution.
String url = conn.getMetaData().getURL();
if (url.equals("jdbc:columnlist:connection")) {
SimpleResultSet rs = new SimpleResultSet();
// With some connection options "id" should be used instead
rs.addColumn("ID", Types.BIGINT, 19, 0);
return rs;
}
// main code
This result set must have columns with exactly the same names and data types as your function normally returns. Be careful with column names, `id` usually means "ID", but if ;DATABASE_TO_LOWER=TRUE or ;DATABASE_TO_UPPER=FALSE were specified in JDBC URL used by your application, it means "id". Your function shouldn't modify any data during this execution, it is only asked about its metadata.
If URL is different, it is a real function call during execution of a query or other command and you need to execute your code.
See also an example:
https://github.com/h2database/h2database/blob/45b609dec0e45125e6a93f85c9018d34551332a1/h2/src/test/org/h2/samples/Function.java#L140

Auto-Increment of Identity in Netbeans Using DerbyDB

I am trying to insert data into a CUSTOMER table.
private void c_enterActionPerformed(java.awt.event.ActionEvent evt) {
String insertSQL = "insert into CUSTOMER(CUST_ID, CUST_NIC, CUST_FNAME,CUST_LNAME, CUST_EMAIL, CUST_ADDRESS, CUST_PHONE, CUST_IMG) values(?,?,?,?,?,?,?,?)";
try{
ps = con.prepareStatement(insertSQL);
ps.setString(1,c_id_text.getText());
ps.setString(2,c_nic_text.getText());
ps.setString(3,c_fname_text.getText());
ps.setString(4,c_lname_text.getText());
ps.setString(5,c_email_text.getText());
ps.setString(6,c_address_text.getText());
ps.setString(7,c_phone_text.getText());
ps.setString(8,img_path_txt.getText());
ps.execute();
JOptionPane.showMessageDialog(null, "New Customer Inserted\nCongratulations!");
c_id_text.setText("");
c_nic_text.setText("");
c_fname_text.setText("");
c_lname_text.setText("");
c_email_text.setText("");
c_address_text.setText("");
c_phone_text.setText("");
img_path_txt.setText("");
updateTable();
}catch(Exception e){
JOptionPane.showMessageDialog(null, "Insertion error: "+e);
}
}
The table was created using:
CREATE TABLE CUSTOMER(
CUST_ID INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
CUST_NIC VARCHAR(14),
CUST_FNAME VARCHAR(20),
CUST_LNAME VARCHAR(25),
CUST_EMAIL VARCHAR(45),
CUST_ADDRESS VARCHAR(60),
CUST_PHONE INTEGER,
CUST_IMG VARCHAR(100));
SELECT * FROM AKASH.CUSTOMER FETCH FIRST 100 ROWS ONLY;
I have disabled the CUST_ID text as shown. It's telling me "Attempt to modify an identity column 'CUST_ID'.
Now, for claritfication: I know what is happening. But I don't know how to fix it.
I tried to remove ps.setString(1,c_id_text.getText()); , that didn't work.
I also tried to remove CUST_ID from String insertSQL... , but to no avail.
If I try to input data from the SQL using "Insert row" button, it works and the CUST_ID column displays ""

Found my mistake. Solved after commenting out
ps.setString(1,c_id_text.getText());
and c_id_text.setText("");
as well as removing CUST_ID form the insertSQL line of code.

JDBC query RETURNING value

I have a problem trying to figure out how to get the id of the last inserted row using PostgreSQL and JDBC.
CREATE TABLE vet_care (
id serial PRIMARY KEY,
deworming int,
castration int
);
My query is
String insertVetCare = "INSERT INTO vet_care(castration,deworming) VALUES("+castrated+","+dewormed+") RETURNING id";
I want the id value (which is serial) for later use. I tried to execute the query like so:
int id = statement.executeUpdate(insertVetCare);
But this says after compilation, that "A result was returned when none was expected." and it does not insert the other values into table.
How can I get this to work?

If "id" means "generated identity key", then you've got it wrong.
The executeUpdate() method returns the number of affected rows, according to the javadocs.
You want it to return auto generated keys, like this.
More advice: Use PreparedStatement and bind values. Building up a SQL query that way is asking for a SQL injection attack.
// Why make the gc work? This query never changes.
private static final String INSERT_VET_CARE = "INSERT INTO vet_care(castration,deworming) VALUES(?, ?)";
PreparedStatement ps = connection.prepareStatement(INSERT_VET_CARE, Statement.RETURN_GENERATED_KEYS);
ps.setInt(1, castration);
ps.setInt(2, deworming);

Java adding data to table using SQL

I am using an sql query to add data data to an existing database table.
I want to add data under the columns 'Room_Resource' and 'Quantity'.
The system is designed to allow bookings and i am trying to add bookings made to a tblBookings table, the code below is taken from JButton clicked function.
The value I want to add to Room_Resource is a name taken from a selected table within the system. I declared a variable for this 'resourceChosenString'
The value I want to add to quantity is from the 'Quantity' variable i have declared in relation to a combo box.
Here are my declarations:
int selectedResourceRow = tblResources.getSelectedRow();
Object resourceChosen = tblResources.getValueAt(selectedResourceRow,1);
String resourceChosenString = resourceChosen.toString();
int Quantity = cmbQuantity.getSelectedIndex();
I then have a sql statement:
String sql = ("INSERT INTO tblBookings (Room_Resource,Quantity) VALUES (" + resourceChosenString + " ', ' " + Quantity + " ',) ");
And then the execute code:
try{
pst = conn.prepareStatement(sql);
pst.execute();
JOptionPane.showMessageDialog(null, "Added");
} catch (Exception e){
JOptionPane.showMessageDialog(null, "Error Adding Booking");
}
Currently it gives me an error when I attempt to add the data to the table and wondered if anyone had any suggestions?
Also I considered that perhaps the problem could lie in the fact I have more than two columns in the external table and the table I am adding the data to so columns could be left blank. If this could be the problem, could anyone tell me how to get around it? Possibly if there is a null function I can use instead of values.

You probably want to tell us what database you're using and what error message you're getting. But just off the bat, it looks like your sql string is not formatted correctly. I don't know if you mistyped it in the question or if your code has a simple syntax error.
Just shooting from the hip with what you have, it looks like your sql statement should be:
String sql = "INSERT INTO tblBookings (Room_Resource,Quantity) VALUES ('" + resourceChosenString + "', " + Quantity + ")";
Notice that resourceChosenString should be wrapped in single quotes (you're missing the single quote on the left). Also, I don't think you're supposed to wrap a number in single quotes (I could be wrong since I don't know which database you're using).
Qwerky is right though; you should use a PreparedStatement.

The SQL you are generating is not valid and looks like this;
INSERT INTO tblBookings (Room_Resource,Quantity) VALUES (resource ', ' 1 ',)
^ ^
missing quote extraneous comma
You should tidy it up, or better still use a PreparedStatement.
String sql = "insert into tblBookings (Room_Resource,Quantity) values (?, ?)";
PreparedStatement pst = conn.prepareStatement(sql);
pst.setString(1, resourceChosenString);
pst.setInt(2, quantity); //variable names are not capitalised by convention
pst.execute();

problem in setString method.in retrieving data from the table

i have two tables "Table1" with columns user_name,Password and course ID and another table "course" with columns course_id,course_name.I have used the following code to display the course ID from Table1 according to the user_name received from the login page.using ResultSet rs1.now i want to retrieve the course_name from the table "course" according to the course ID receieve from "Table1".for that in the second query pstmt2.setString(1, ); what parameter i should use to get the course_id value from the previous query
HttpSession sess=request.getSession();
String a=(String)sess.getAttribute("user");
String b=(String)sess.getAttribute("pass");
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection con=DriverManager.getConnection("jdbc:odbc:ggg");
Statement st = con.createStatement();
String query="select * from Table1 where user_name=?";
PreparedStatement pstmt=con.prepareStatement(query);
pstmt.setString(1,a);
ResultSet rs1=pstmt.executeQuery();
while(rs1.next())
out.println("<h3>COURSE ID: "+rs1.getString("course ID")+"<h3>");
String query2="SELECT * from course where course_id=?";
PreparedStatement pstmt2=con.prepareStatement(query2);
pstmt2.setString(1,);
ResultSet rs2=pstmt2.executeQuery();
while(rs2.next())
{
out.println("<h3>course name: "+rs2.getString("course_name")+"<h3>");
}

why do you go for two turns of database hit, even though you created one time connection object.
modify the query as below
SELECT * from course where course_id = (select course_id from Table1 where user_name=?);
from this query you noneed to give input of courseid also.

No need to hit database twice to get the results that you need. use the query
Select table1.course_id, course.course_name from table1, course where table1.course_id=course_id and table1.user_name=?

This should set the course_id parameter:
pstmt2.setString(1,rs1.getString("course_id"));
Or, as I see the "course_id" column may have a different name in "Table1":
pstmt2.setString(1,rs1.getString("course ID"));

As the other post mentioned there's no need to go to another set of query. Try this example query:
SELECT course.course_id, course.course_name
FROM table1 t1
INNER JOIN course c
ON t1.course_id = c.course_id
WHERE t1.user_name = ?;
Now if you insist your coding the parameter o your pstmt2.setString(1,); is:
pstmt2.setString(1,rs1.getString("course_id")); //or course ID defending on your column name