How to Add a Default Value to a Column in Snowflake

When working with Snowflake, one common task you might encounter is adding a default value to a column. This ensures that if no value is provided during an insert, a predefined default value will be used instead. In this tutorial, we'll guide you through the process of adding default values to columns in Snowflake with easy-to-follow instructions.

Why Add Default Values?

Adding default values to columns is useful for ensuring that data inserted into your table adheres to specific standards. It can help avoid null values or ensure that certain columns always have a meaningful value even when not explicitly specified. For example, you might want to set a default status of "active" for a user or set the default currency to USD in an order table.

Syntax for Adding Default Values

To add a default value to an existing column in Snowflake, you use the following syntax:

ALTER TABLE table_name MODIFY COLUMN column_name SET DEFAULT default_value;

Where:

• table_name is the name of the table you are modifying.
• column_name is the name of the column where the default will be applied.
• default_value is the value that will be inserted when no other value is provided.

Example: Adding a Default Value to a Column

Let's say we have a table called users and we want to add a default value of "active" to the status column. Here's how you can do it:

ALTER TABLE users MODIFY COLUMN status SET DEFAULT 'active';

This will set the default value for the status column to "active" whenever a new record is inserted and no value is provided for the status field.

Checking the Default Value

To verify the default value, you can use the SHOW COLUMNS command to inspect the table's structure:

SHOW COLUMNS IN users;

This will display the column details, including the default value for the status column.

Conclusion

Adding default values to columns in Snowflake is a simple yet powerful feature that can ensure data integrity and reduce the risk of missing or invalid data. By using the ALTER TABLE statement, you can easily set default values for existing columns in your tables. Remember that default values should align with your database design and business rules to ensure they are meaningful and useful.