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create table table_name (id number, column_name varchar2(4));
select column_name, data_type, data_default from user_tab_columns;
| COLUMN_NAME | DATA_TYPE | DATA_DEFAULT |
|---|---|---|
| ID | NUMBER | null |
| COLUMN_NAME | VARCHAR2 | null |
insert into table_name (id) values (1);
1 rows affected
alter table table_name modify column_name default '0000';
select column_name, data_type, data_default from user_tab_columns;
| COLUMN_NAME | DATA_TYPE | DATA_DEFAULT |
|---|---|---|
| ID | NUMBER | null |
| COLUMN_NAME | VARCHAR2 | '0000' |
insert into table_name (id) values (2);
1 rows affected
alter table table_name modify column_name default NuLl;
select column_name, data_type, data_default from user_tab_columns;
| COLUMN_NAME | DATA_TYPE | DATA_DEFAULT |
|---|---|---|
| ID | NUMBER | null |
| COLUMN_NAME | VARCHAR2 | NuLl |
insert into table_name (id) values (3);
1 rows affected
select * from table_name;
| ID | COLUMN_NAME |
|---|---|
| 1 | null |
| 2 | 0000 |
| 3 | null |