Autogenerated key

Question

I can connect to my database through jdbc, run queries, etc. Now I need to be able to add rows to a table. However, I have a primary key that is an autogenerated number, and I don't know what to pass in the variable.
My update string is as follows:
=============================================
UPDATE_STRING = "INSERT INTO PPAL_LOGS " +
"VALUES ('" + LOG_SEQ_ID + "', '" + PPA_NBR + "', '" + FILE_TIME_STAMP + "', '" + DATE_PROCESSED +
"', '" + PROCESSED_FLAG + "', '" + FILE_NAME + "')";
=============================================
My autogenerated, numeric key is LOG_SEQ_ID. What should the value of this be? Thanks for your help!

Answer 1

Assuming that LOG_SEQ_ID the name of the primary key column in you PPAL_LOGS table, and is also the name of an Oracle sequence, you have two options. First, if you need the key at the same time you insert a row into your table in order to insert rows into a child table, then allocate a sequence by executing the following SQL statement before your insert:
Integer log_seq_id;
ResultSet rset = conn.executeQuery(
"select LOG_SEQ_ID.nextval from DUAL");
rset.next();
log_seq_id = rset.getInteger(1);
then use log_seq_id in your insert statement.
If you don't need to know the value of your LOG_SEQ_ID, or this is a table that you do a lot of loading of external data, then you can create a trigger on the table in the database to automatically allocate a sequence when the LOG_SEQ_ID column is null like so:
create or replace trigger PPAL_LOGS_BIR
before insert on PPAL_LOGS
for each row
begin
if :new.LOG_SEQ_ID is null then
begin
select LOG_SEQ_ID.nextval
into :new.LOG_SEQ_ID
from SYS.DUAL;
exception
when OTHERS then
raise_application_error( -20000,
SQLERRM| |
' on select LOG_SEQ_ID.nextval'| |
' in PPAL_LOGS_BIR' );
end;
end if;
end;
Once a trigger like this is in place, any time you specify a null for LOG_SEQ_ID, the trigger will allocate a new sequence and assign it to the column for you while it is inserting the row into the table.