When performing an UPDATE statement you may get this error message:
 Unable to get a stable set of rows in the source tables (Session: )
This is because when EXASOL is performing the UPDATE, under the covers it is really doing a MERGE. You can read more about this in Chapter 2 of the Exasol manual, but the highlight is as follows:
Internally, this statement is transformed into a MERGE statement. Therefore, error
messages can refer to the MERGE command. If one row is updated multiple times,
the new value must be identical. Otherwise you will get the error message “Unable
to get a stable set of rows in the source tables”.
Essentially, make sure that a row is only being updated once.