Convert from VARCHAR2 to NCLOB (oracle)

I got a column message with data_type = VARCHAR2. It already has some data stored. I want this column to be of type NCLOB. Code-Set for this column should be UTF-8.

I did the following:

• added a column tempmessage to my table of type NCLOB
• filled tempmessage with message
• renamed message to message old (so that i don't use any data (until it works))
• renamed tempmessage to message

Then i tried out my integration tests and i got the exception: java.sql.BatchUpdateException: ORA-01400: Insert of NULL into ("BATCH_LOG"."MESSAGEOLD") not possible.

What have I done wrong?

The original column was defined as NOT NULL, when you renamed that to MESSAGEOLD, this constraint was kept. You need to remove the NOT NULL constraint from the MESSAGEOLD column:

ALTER TABLE foo MODIFY MESSAGEOLD NULL;