Comdb2 Postgres SQL Equivalents

What would be the equivalents of the following PostgresSQL constructs in ComDB2. I've consulted the documentation and could not find it(These are related to `CREATE TABLE` statements):

1. `DEFAULT CURRENT_TIMESTAMP`: Setting a timestamp(or any) column default value
2. `UNIQUE`: Applying a unique constraint
3. `o_carrier_id int NULL DEFAULT NULL`
4. `decimal(6, 2)`: I actually tried `decimal32` for this but it throws the following error log
`incompatible values from SQL real '5.000000' to decimal field 'ol_quantity' for table 'order_line'`.