# ADD COLUMN

The `ADD COLUMN` statement is part of `ALTER TABLE` and adds columns to tables.

## Synopsis

## Required privileges

The user must have the `CREATE` privilege on the table.

## Parameters

Parameter | Description
--- | ---
`table_name` | The name of the table to which you want to add the column.
`column_name` | The name of the column you want to add. The column name must follow these identifier rules and must be unique within the table but can have the same name as indexes or constraints.
`typename` | The data type of the new column.
`col_qualification` | An optional list of column definitions, which may include column-level constraints, collation, or column family assignments. If the column family is not specified, the column will be added to the first column family. For more information about how column families are assigned, see Column Families. Note that it is not possible to add a column with the foreign key constraint. As a workaround, you can add the column without the constraint, then use `CREATE INDEX` to index the column, and then use `ADD CONSTRAINT` to add the foreign key constraint to the column.

## Viewing schema changes

Whenever you initiate a schema change, CockroachDB registers it as a job, which you can view with `SHOW JOBS`.

## Examples

### Add a single column

    > ALTER TABLE accounts ADD COLUMN names STRING;

    > SHOW COLUMNS FROM accounts;

    +-------------+-----------+-------------+----------------+-----------------------+-------------+
    | column_name | data_type | is_nullable | column_default | generation_expression |   indices   |
    +-------------+-----------+-------------+----------------+-----------------------+-------------+
    | id          | INT       |    false    | NULL           |                       | {"primary"} |
    | balance     | DECIMAL   |    true     | NULL           |                       | {}          |
    | names       | STRING    |    true     | NULL           |                       | {}          |
    +-------------+-----------+-------------+----------------+-----------------------+-------------+
    (3 rows)

### Add multiple columns

    > ALTER TABLE accounts ADD COLUMN location STRING, ADD COLUMN amount DECIMAL;

    > SHOW COLUMNS FROM accounts;

    +-------------+-----------+-------------+----------------+-----------------------+-------------+
    | column_name | data_type | is_nullable | column_default | generation_expression |   indices   |
    +-------------+-----------+-------------+----------------+-----------------------+-------------+
    | id          | INT       |    false    | NULL           |                       | {"primary"} |
    | balance     | DECIMAL   |    true     | NULL           |                       | {}          |
    | names       | STRING    |    true     | NULL           |                       | {}          |
    | location    | STRING    |    true     | NULL           |                       | {}          |
    | amount      | DECIMAL   |    true     | NULL           |                       | {}          |
    +-------------+-----------+-------------+----------------+-----------------------+-------------+
    (5 rows)

### Add a column with a `NOT NULL` constraint and a `DEFAULT` value

    > ALTER TABLE accounts ADD COLUMN interest DECIMAL NOT NULL DEFAULT (DECIMAL '1.3');

    > SHOW COLUMNS FROM accounts;

    +-------------+-----------+-------------+------------------------+-----------------------+-------------+
    | column_name | data_type | is_nullable |     column_default     | generation_expression |   indices   |
    +-------------+-----------+-------------+------------------------+-----------------------+-------------+
    | id          | INT       |    false    | NULL                   |                       | {"primary"} |
    | balance     | DECIMAL   |    true     | NULL                   |                       | {}          |
    | names       | STRING    |    true     | NULL                   |                       | {}          |
    | location    | STRING    |    true     | NULL                   |                       | {}          |
    | amount      | DECIMAL   |    true     | NULL                   |                       | {}          |
    | interest    | DECIMAL   |    false    | 1.3:::DECIMAL::DECIMAL |                       | {}          |
    +-------------+-----------+-------------+------------------------+-----------------------+-------------+
    (6 rows)

### Add a column with `NOT NULL` and `UNIQUE` constraints

    > ALTER TABLE accounts ADD COLUMN cust_number DECIMAL UNIQUE NOT NULL;

### Add a column with collation

    > ALTER TABLE accounts ADD COLUMN more_names STRING COLLATE en;

### Add a column and assign it to a column family

#### Add a column and assign it to a new column family

    > ALTER TABLE accounts ADD COLUMN location1 STRING CREATE FAMILY new_family;

#### Add a column and assign it to an existing column family

    > ALTER TABLE accounts ADD COLUMN location2 STRING FAMILY existing_family;

#### Add a column and create a new column family if column family does not exist

    > ALTER TABLE accounts ADD COLUMN new_name STRING CREATE IF NOT EXISTS FAMILY f1;

## See also

- `ALTER TABLE`
- Column-level Constraints
- Collation
- Column Families