Removing Default Values in Oracle: A Quick Guide（oracle删除默认值）

Database administrators quite often need to perform updates to their Oracle database, particularly when changing or removing default values. Removing default values is one such task. Default values are user-defined values that are used by the Oracle database server to set systemwide options. In this article, we’ll cover some tips on how to quickly and easily remove default values in Oracle databases.

When it comes to removing default values in Oracle, there are two methods that can be employed. The first method is to use the ALTER SYSTEM command. This command is used to modify the properties of the Oracle instance, including default values. To remove a default value using the ALTER SYSTEM command, the following syntax can be employed:

ALTER SYSTEM SET ='';

For example, if we needed to remove the default value for “db_name” in our Oracle database, we could use the following command:

ALTER SYSTEM SET db_name='';

The second method for removing default values in Oracle is to use the ALTER DATABASE command. This command is used to modify the properties of a specific database. To remove a default value using the ALTER DATABASE command, you can use the following syntax:

ALTER DATABASE  SET ='';

For example, if we needed to remove the default value for “sys_timestamp” in our Oracle database, we could use the following command:

ALTER DATABASE  SET sys_timestamp='';

It is worth noting that before attempting to remove default values in Oracle, it is always a good idea to ensure that no other system-wide settings are dependent on the value being removed. This can be accomplished by reviewing the dependencies tab in Oracle Enterprise Manager. Additionally, it is a good idea to back up your database before attempting to remove any default values.

All in all, removing default values in Oracle databases is a relatively straightforward task. The two primary methods for removing default values are the ALTER SYSTEM and ALTER DATABASE commands. It is important, however, to ensure that no other system-wide settings are dependent on the value being removed and to back up your database before attempting to make any changes.