Prior to 12c, the DEFAULT for a column would not be applied if you explicitly (or implicitly) inserted a NULL into that column. The NULL would override the DEFAULT value -- the DEFAULT would not get applied. However, 12c has introduced a DEFAULT ON NULL clause.

Is Oracle column nullable by default?

If the column is referenced, even when supplying the value NULL, the default value is not used. Oracle 12c allows you to modify this behaviour using the ON NULL clause in the default definition. The following example compares the default action of the DEFAULT clause, with that of DEFAULT ON NULL .

Is null or empty in Oracle?

Answer: An empty string is treated as a null value in Oracle.