How can a default timestamp be added to an existing table in Snowflake by creating a new column?

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To add a default timestamp column to an existing table in Snowflake, you can use the ALTER TABLE command with the ADD COLUMN clause as follows:

ALTER TABLE table_name ADD COLUMN new_column_name TIMESTAMP DEFAULT CURRENT_TIMESTAMP;

Here, "tablename" is the name of the table where the new column will be added, "newcolumnname" is the name you want to give to the new column, "TIMESTAMP" is the data type of the column, and "DEFAULT CURRENTTIMESTAMP" sets the default value of the column to the current system timestamp.