After upgrading to TOAD 13 I noticed the generated scripts were different for ‘not null’ named constraints.
ALTER TABLE LBS_ACTION_JN MODIFY
JN_OPERATION CONSTRAINT LBS_ACTIONJN_OPER_NCHK NOT NULL
ALTER TABLE LBS_ACTION_JN ADD (
CHECK (“JN_OPERATION” IS NOT NULL)
The second script adds a constraint but does not make the column ‘not null’ in the table description.
Found this post which explains the difference: