Question

Please have a look at the following code

package normal;

//This class if s for checking the database. If the database doesn't exists, this class will create one

import java.sql.*;

public class DatabaseCheck
{
    private Connection con;

    public DatabaseCheck()
    {
        createConnection();
        try
        {
            Statement st = con.createStatement();
            st.executeQuery("select * from PhoneData");
        }
        catch(Exception e)
        {
            System.out.println(e.getLocalizedMessage());

            if(e.getLocalizedMessage().equals("Schema 'SA' does not exist"))
            {
                try
                {
                PreparedStatement ps = con.prepareStatement("create table PhoneData(ids int identity constraint pkId primary key,names varchar(20),mobileNumber1 varchar(20),mobileNumber2 varchar(20),landNumber1 varchar(20),landNumber2 varchar(20),address varchar(100),category varchar(20),nickName varchar(20),email varchar(20),middleName varchar(20),lastName varchar(20),city varchar(20),country varchar(20))");
                ps.execute();

                PreparedStatement ps2 = con.prepareStatement("create table Emails(accountType varchar(10) constraint pk_user primary key,userName varchar(50) ,passwords varchar(50))");
                ps2.execute();

                }
                catch(Exception e2)
                {
                    e2.printStackTrace();
                }
            }
        }
        finally
        {
            closeConnection();
        }
    }

     public void createConnection()
    {
        try
        {
            Class.forName("org.apache.derby.jdbc.EmbeddedDriver");

            con = DriverManager.getConnection("jdbc:derby:PhoneBook;create=true","sa","sasasa");
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }

      public void closeConnection()
    {
        try
        {
            con.close();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
}

This class is capable of programmatically creating tables in embedded apache derby database. But, it gives the following error

java.sql.SQLSyntaxErrorException: Syntax error: Encountered "identity" at line 1, column 32.
    at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown Source)
    at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedPreparedStatement.<init>(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedPreparedStatement20.<init>(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedPreparedStatement30.<init>(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedPreparedStatement40.<init>(Unknown Source)
    at org.apache.derby.jdbc.Driver40.newEmbedPreparedStatement(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown Source)
    at normal.DatabaseCheck.<init>(DatabaseCheck.java:27)
    at normal.MyPhoneBookApp.main(MyPhoneBookApp.java:25)
Caused by: java.sql.SQLException: Syntax error: Encountered "identity" at line 1, column 32.
    at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown Source)
    ... 15 more
Caused by: ERROR 42X01: Syntax error: Encountered "identity" at line 1, column 32.
    at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
    at org.apache.derby.impl.sql.compile.ParserImpl.parseStatement(Unknown Source)
    at org.apache.derby.impl.sql.GenericStatement.prepMinion(Unknown Source)
    at org.apache.derby.impl.sql.GenericStatement.prepare(Unknown Source)
    at org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(Unknown Source)
    ... 9 more

When I remove the “identity” keyword from the table creation code, this work fine. But, auto generation of ID’s is mandatory. Please help!

Answer 1

Derby has no identity column type (as documented in the manual). You need to define a generated column. For the generation definition, Derby indeed knows an identity attribute, but that’s not a datatype.

So the column definition for ids should be

ids integer generated always as identity constraint pkId primary key

Note that you can also use generated by default instead of always. Then a value will only be generated if you don’t specify a value for that column during insert. generated always will overwrite any value you provide.