How to Add a Column in Snowflake

In this tutorial, we will walk you through the process of adding a new column to an existing table in Snowflake. Adding a column to a table is a common task when modifying the schema of your data warehouse, and Snowflake makes it straightforward with its ALTER TABLE command.

Prerequisites

Before adding a column, ensure that you have the necessary privileges to alter the table. You need the OWNERSHIP privilege or the ALTER privilege on the target table.

Step 1: Connect to Your Snowflake Account

Start by connecting to your Snowflake instance using your preferred SQL client or the Snowflake Web UI. Once logged in, select the database and schema where the table is located.

Step 2: Use the ALTER TABLE Command

To add a new column, use the ALTER TABLE SQL command. The basic syntax is as follows:

ALTER TABLE table_name ADD COLUMN column_name column_type;

For example, if you want to add a column called new_column of type VARCHAR to a table called employee, you would run:

ALTER TABLE employee ADD COLUMN new_column VARCHAR;

Step 3: Verify the Column Addition

After running the ALTER TABLE command, you can verify the addition of the column by querying the INFORMATION_SCHEMA.COLUMNS view:

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'employee';

This will return a list of columns in the employee table, including the newly added column.

Step 4: (Optional) Set a Default Value for the New Column

If you want the new column to have a default value for all existing rows, you can modify the column using the SET DEFAULT clause:

ALTER TABLE employee ADD COLUMN new_column VARCHAR DEFAULT 'N/A';

Conclusion

Adding a column to a Snowflake table is a simple and efficient process. With the ALTER TABLE command, you can easily modify your schema to accommodate new data requirements. Make sure to verify your changes and consider setting default values as needed.