In order to get the default value to kick in in an insert statement (which I assume you're trying to do), you can either omit that column name from the insert list or set that column value to DEFAULT (no quotes)
There is a column in my table with not null constraint. Default value is set to 0 for that column. In my query, column value is set to null. When i try to execute that query in pgsql, it is getting failed due to constraint violation. Any idea? This is working in oracle.