Native query. How to get the data...

Question

Hello everyone!
I'm struggling to figure out how to extract data from particular columns from DB. Here is what I have...
A table PersData with columns A, B, C, D and so forth. Also there is an entity represents this table called PersonalData.
I need to get the data from A and C columns, but I still haven't found a solution how to do this. I know how to exctract an entire row from the PersData table by writing the following code...
Query query = entityManager.createNativeQuery("SELECT * FROM 'PersData` ", PersonalData.class);
List<PersonalData> qresult = query.getResultList();
for(PersonalData item: qresult){
      System.out.println(item.getA());
      ........ But it's inefficient to get values of other columns at the same time.
I guess that my query should be written smth like this...
Query query = entityManager.createNativeQuery("SELECT A, C FROM `PersData` ");
List<PersonalData> qresult = query.getResultList();
for(PersonalData item: qresult){
      System.out.println(item.getA());
      .....But I got an error java.lang.ClassCastException when I do this for (PersonalData item: qresult). Actually, I understand why it's like this.
Does anybody know how to get values just from two columns and then use them?

Answer 1

Oops, my bad. it was about 2 paragraphs further
down...
"autoGeneratedKeys - a constant indicating whether
auto-generated keys should be made available for
retrieval using the method getGeneratedKeys;"Down in what?
The following is the docs for the method you posted taken from here - http://java.sun.com/j2se/1.4.2/docs/api/java/sql/Statement.html#executeUpdate(java.lang.String, int).
executeUpdate
public int executeUpdate(String sql,
int autoGeneratedKeys)
throws SQLException
Executes the given SQL statement and signals the driver with the given flag about whether the auto-generated keys produced by this Statement object should be made available for retrieval.
Parameters:
sql - must be an SQL INSERT, UPDATE or DELETE statement or an SQL statement that returns nothing
autoGeneratedKeys - a flag indicating whether auto-generated keys should be made available for retrieval; one of the following constants: Statement.RETURN_GENERATED_KEYS Statement.NO_GENERATED_KEYS
Returns:
either the row count for INSERT, UPDATE or DELETE statements, or 0 for SQL statements that return nothing
Throws:
SQLException - if a database access error occurs, the given SQL statement returns a ResultSet object, or the given constant is not one of those allowed
Since:
1.4
I don't see the text you posted in there.
At the very least there is at least a suggestion that an exception will be or could be thrown because the only way some databases can return an autogenerated key is via a result set.