I have workflows that submit UPDATE, INSERT or DELETE SQL statements to my oracle database by means of the database reader and the database looping nodes. Most of the time this works without any problems, but I notice that If I have had the KNIME program open for more than few hours, these nodes will start to fail with a "ERROR Database Looping 3:38:32 Execute failed: ORA-00900: invalid SQL statement" error.
If I save everything and restart KNIME, the problem goes away initially (using the exact same inputs) and then comes back once KNIME has been open for awhile. I can't get a reproducible set of circumstances to trigger this -- it really seems to be the case that it is dependent on how long KNIME has been open or perhaps how much toal KNIME activity has gone on since the last KNIME restart.
Is there anything intrisically different about using UPDATE or DELETE statements (as opposed to just SELECT) that could cause this behavior? I am using KNIME 3.1.2, but have observed this behavior for all versions back to 12.9.x.
[BTW: I am aware of the databse update and database delete nodes and I use those where appropriate, but sometimes you need to run an SQL update, insert or delete statement directly]