How to Remove a Default Value to a Column in Snowflake

In Snowflake, removing a default value from a column involves modifying the column’s definition within a table. This operation may be necessary when you need to stop using a default value for new records or to adjust the behavior of your database schema.

Step 1: Understanding Default Values in Snowflake

In Snowflake, columns can have default values that are applied when new rows are inserted into a table. This can simplify data entry by automatically providing a value for certain columns. However, there are situations where you may want to remove a default value.

Step 2: Alter the Column to Remove the Default Value

To remove a default value from a column in Snowflake, you can use the ALTER TABLE statement. Here’s the syntax for removing a default value:

ALTER TABLE table_name MODIFY COLUMN column_name SET DEFAULT NULL;

This command modifies the specified column by setting its default value to NULL, effectively removing any previously set default value.

Step 3: Verifying the Change

Once you’ve executed the ALTER statement, it’s important to verify that the default value has been removed. You can use the SHOW COLUMNS command to inspect the column’s definition:

SHOW COLUMNS IN TABLE table_name;

Check the DEFAULT column in the output to ensure it is now set to NULL.

Step 4: Example

Let’s say you have a table called employees and you want to remove the default value from the hire_date column:

ALTER TABLE employees MODIFY COLUMN hire_date SET DEFAULT NULL;

After executing this statement, the hire_date column will no longer have a default value, and new records will require an explicit value for this column.

Conclusion

Removing a default value from a column in Snowflake is straightforward using the ALTER TABLE statement. It’s important to verify that the change has been successfully applied by inspecting the column’s definition. By following these steps, you can easily modify your database schema to meet your changing requirements.