To see the default values in a table in Oracle, you can query the USER_TAB_COLS view. This view contains information about the columns in all tables that are accessible to the current user. When querying this view, you can look at the DATA_DEFAULT column to see the default value defined for each column in the table.
Here is an example query that you can use to see the default values in a table:
SELECT COLUMN_NAME, DATA_DEFAULT FROM USER_TAB_COLS WHERE TABLE_NAME = 'YourTableName';
Replace 'YourTableName' with the name of the table for which you want to see the default values. This query will return the column name along with its default value for the specified table.
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How to ensure that default values are properly maintained in Oracle tables over time?
- Use constraints: Define default values using constraints in the CREATE TABLE or ALTER TABLE statements. This will ensure that the default values are enforced at the database level and cannot be overridden.
- Regularly check and validate default values: Periodically review the default values in your tables to ensure they are still appropriate and accurate. This can be done through data profiling or querying the data dictionary views in Oracle.
- Document default values: Maintain documentation that outlines the default values for each column in your tables. This will make it easier for developers and DBAs to understand and maintain the default values over time.
- Use triggers: Implement triggers to enforce default values for specific columns in your tables. This can provide additional control and flexibility in managing default values.
- Conduct regular data quality checks: Monitor the data in your tables to ensure that default values are being correctly applied and maintained. This can help identify and address any issues with default values not being enforced properly.
- Implement data governance policies: Establish data governance policies and procedures that outline how default values should be managed and maintained in your Oracle tables. This can help ensure consistency and accuracy in default values across your organization.
How to display the default values set in a table in Oracle database?
You can display the default values set in a table in an Oracle database by querying the USER_TAB_COLUMNS data dictionary view.
Here is an example query to display the default values set in a table named your_table_name:
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SELECT COLUMN_NAME, DATA_DEFAULT FROM USER_TAB_COLUMNS WHERE TABLE_NAME = 'your_table_name'; |
This query will return the column names and their default values for the specified table. If a column does not have a default value set, the DATA_DEFAULT column will be null.
What is the restriction on altering default values in Oracle tables?
In Oracle, after a table has been created, the default values assigned to columns cannot be altered directly using the ALTER TABLE statement. If you need to change the default value of a column, you would need to drop and re-create the default constraint on that column.
