The first step is to query all fields of a table:
select * from dba_tab_columns t where t.TABLE_NAME='T_CCCPT'
The result is as follows:
Analysis found that the NULLABLE column has indicated which fields are allowed to be empty and which fields are not allowed to be empty, which are represented by Y and N respectively.
From this, we can know that if we need to query whether the OBJECTID field is allowed to be empty, use the following statement:
select t.NULLABLE from dba_tab_columns t where t.TABLE_NAME='T_CCCPT' and t.COLUMN_NAME='OBJECTID'
The result is as follows:
in line with our expectations.