Getting a Mysql auto increment value back into my Java cli..

Hello,

I'm busy developing a Java GUI client/server database application with
Netbeans IDE 6.0 and
Mysql to automate the data management and other tasks for my Dongo
website
(see http://www.dongo.org to get an idea what is the targeted result
of all
my programming). I have a question as described below.

To insert a country in my mysql country table I use the code below
which is working fine:

private static void countryInsert(Country country) {
if (country.isValid())
try {
String sqlString = "INSERT INTO country VALUES(0, '" +
country.getCode();
sqlString += "', '" + country.getName() + "')";
sqlStatement.executeUpdate(sqlString);
} catch (SQLException ex) {
Logger.getLogger(Objectbase.class.getName()).log(Level.SEVERE,
null, ex);
}
}

The first column sid of the country table (as for all my tables) is
auto increment:

| sid | bigint(20) unsigned | NO | PRI | NULL | auto_increment
|

I would like to get the value assigned to sid by Mysql back into my
client Java application
preferably with the one sql statement I'm already using to insert.
Only if really necessary
with a second sql statement. What is the best way to programm this?

Thanks and best regards :c),

BoBi

BoBi wrote:
> Hello,
>
> I'm busy developing a Java GUI client/server database application with
> Netbeans IDE 6.0 and
> Mysql to automate the data management and other tasks for my Dongo
> website
> (see http://www.dongo.org to get an idea what is the targeted result
> of all
> my programming). I have a question as described below.
>
> To insert a country in my mysql country table I use the code below
> which is working fine:
>
> private static void countryInsert(Country country) {
> if (country.isValid())
> try {
> String sqlString = "INSERT INTO country VALUES(0, '" +
> country.getCode();
> sqlString += "', '" + country.getName() + "')";
> sqlStatement.executeUpdate(sqlString);
> } catch (SQLException ex) {
> Logger.getLogger(Objectbase.class.getName()).log(Level.SEVERE,
> null, ex);
> }
> }
>
> The first column sid of the country table (as for all my tables) is
> auto increment:
>
> | sid | bigint(20) unsigned | NO | PRI | NULL | auto_increment
> |
>
> I would like to get the value assigned to sid by Mysql back into my
> client Java application
> preferably with the one sql statement I'm already using to insert.
> Only if really necessary
> with a second sql statement. What is the best way to programm this?

The best solution is to use Connection.prepareStatement(String sql, int
autoGeneratedKeys) to create a prepared statement:

String sqlString = "INSERT INTO country(countryCode,countryName)
VALUES(?,?)";

PreparedStatement pstmt = conn.prepareStatement(sqlString,
Statement.RETURN_GENERATED_KEYS);

assuming that your table has columns named countryCode and countryName
to store the country code and name respectively.

Then insert a row using code such as

pstmt.setString(1, country.getCode());
pstmt.setString(2, country.getName());

int rc = pstmt.executeUpdate();

// rc is the number of rows actually inserted

and retrieve the auto_increment value generated by the server like this:

ResultSet rs = pstmt.getGeneratedKeys();

int sid = rs.next() ? rs.getInt(1) : -1;

rs.close();

The use of a prepared statement is also preferable to hard-coding quotes
into an SQL query string as you did in your code snippet.

You can also re-use the prepared statement to insert further rows, for
as long as the parent connection remains open. All in all, prepared
statements are a more elegant, flexible and secure approach, as well as
providing a convenient way to get auto_increment values.

David Harper
Cambridge, England