How to Add a Column in ClickHouse

To add a column to a table in ClickHouse, use the ALTER TABLE statement in combination with ADD COLUMN.

This example adds the column my_new_column of type TEXT to the existing table my_table:

ALTER TABLE my_table ADD COLUMN my_new_column TEXT;

Include the IF NOT EXISTS clause if you don’t want the query to return an error in case my_new_colum already exists:

ALTER TABLE my_table ADD COLUMN IF NOT EXISTS my_new_column TEXT;

Adding Multiple Columns

You can also add multiple new columns at once:

ALTER TABLE my_table
ADD COLUMN my_new_column_1 TEXT,
ADD COLUMN my_new_column_2 BOOLEAN;

This example defines a default value of 'hello' for the new column.

ALTER TABLE my_table ADD COLUMN my_new_column TEXT DEFAULT 'hello';