ADD COLUMN

ADD COLUMN is a subcommand of ALTER TABLE. Use ADD COLUMN to add columns to existing tables.

Tip:

This command can be combined with other ALTER TABLE commands in a single statement. For a list of commands that can be combined, see ALTER TABLE. For a demonstration, see Add and rename columns atomically.

Synopsis

ALTER TABLE IF EXISTS table_name ADD COLUMN IF NOT EXISTS column_name typename col_qualification

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 qualifications.

Viewing schema changes

This schema change statement is registered as a job. You can view long-running jobs with SHOW JOBS.

Examples

Setup

The following examples use the bank demo database schema.

To follow along, run cockroach demo bank to start a temporary, in-memory cluster with the bank schema and dataset preloaded:

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$ cockroach demo bank

Add a single column

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> ALTER TABLE bank ADD COLUMN active BOOL;
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> SHOW COLUMNS FROM bank;
  column_name | data_type | is_nullable | column_default | generation_expression |  indices  | is_hidden
--------------+-----------+-------------+----------------+-----------------------+-----------+------------
  id          | INT8      |    false    | NULL           |                       | {primary} |   false
  balance     | INT8      |    true     | NULL           |                       | {}        |   false
  payload     | STRING    |    true     | NULL           |                       | {}        |   false
  active      | BOOL      |    true     | NULL           |                       | {}        |   false
(4 rows)

Add multiple columns

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> ALTER TABLE bank ADD COLUMN location STRING, ADD COLUMN currency STRING;
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> SHOW COLUMNS FROM bank;
  column_name | data_type | is_nullable | column_default | generation_expression |  indices  | is_hidden
--------------+-----------+-------------+----------------+-----------------------+-----------+------------
  id          | INT8      |    false    | NULL           |                       | {primary} |   false
  balance     | INT8      |    true     | NULL           |                       | {}        |   false
  payload     | STRING    |    true     | NULL           |                       | {}        |   false
  active      | BOOL      |    true     | NULL           |                       | {}        |   false
  location    | STRING    |    true     | NULL           |                       | {}        |   false
  currency    | STRING    |    true     | NULL           |                       | {}        |   false
(6 rows)

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

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> ALTER TABLE bank ADD COLUMN interest DECIMAL NOT NULL DEFAULT (DECIMAL '1.3');
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> SHOW COLUMNS FROM bank;
  column_name | data_type | is_nullable |     column_default     | generation_expression |  indices  | is_hidden
--------------+-----------+-------------+------------------------+-----------------------+-----------+------------
  id          | INT8      |    false    | NULL                   |                       | {primary} |   false
  balance     | INT8      |    true     | NULL                   |                       | {}        |   false
  payload     | STRING    |    true     | NULL                   |                       | {}        |   false
  active      | BOOL      |    true     | NULL                   |                       | {}        |   false
  location    | STRING    |    true     | NULL                   |                       | {}        |   false
  currency    | STRING    |    true     | NULL                   |                       | {}        |   false
  interest    | DECIMAL   |    false    | 1.3:::DECIMAL::DECIMAL |                       | {}        |   false
(7 rows)

Add a column with a UNIQUE constraint

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> ALTER TABLE bank ADD COLUMN address STRING UNIQUE;
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> SHOW COLUMNS FROM bank;
  column_name | data_type | is_nullable |     column_default     | generation_expression |          indices           | is_hidden
--------------+-----------+-------------+------------------------+-----------------------+----------------------------+------------
  id          | INT8      |    false    | NULL                   |                       | {primary,bank_address_key} |   false
  balance     | INT8      |    true     | NULL                   |                       | {}                         |   false
  payload     | STRING    |    true     | NULL                   |                       | {}                         |   false
  active      | BOOL      |    true     | NULL                   |                       | {}                         |   false
  location    | STRING    |    true     | NULL                   |                       | {}                         |   false
  currency    | STRING    |    true     | NULL                   |                       | {}                         |   false
  interest    | DECIMAL   |    false    | 1.3:::DECIMAL::DECIMAL |                       | {}                         |   false
  address     | STRING    |    true     | NULL                   |                       | {bank_address_key}         |   false
(8 rows)

Add a column with a FOREIGN KEY constraint

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> CREATE TABLE customers (
  id INT PRIMARY KEY,
  name STRING
);
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> ALTER TABLE bank ADD COLUMN cust_number INT REFERENCES customers(id);
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> SHOW COLUMNS FROM bank;
  column_name | data_type | is_nullable | column_default | generation_expression |          indices           | is_hidden
--------------+-----------+-------------+----------------+-----------------------+----------------------------+------------
  id          | INT8      |    false    | NULL           |                       | {primary,bank_address_key} |   false
  balance     | INT8      |    true     | NULL           |                       | {}                         |   false
  payload     | STRING    |    true     | NULL           |                       | {}                         |   false
  active      | BOOL      |    true     | NULL           |                       | {}                         |   false
  location    | STRING    |    true     | NULL           |                       | {}                         |   false
  currency    | STRING    |    true     | NULL           |                       | {}                         |   false
  interest    | DECIMAL   |    false    | 1.3:::DECIMAL  |                       | {}                         |   false
  address     | STRING    |    true     | NULL           |                       | {bank_address_key}         |   false
  cust_number | INT8      |    true     | NULL           |                       | {}                         |   false
(9 rows)
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> SHOW CONSTRAINTS FROM bank;
  table_name |       constraint_name        | constraint_type |                      details                       | validated
-------------+------------------------------+-----------------+----------------------------------------------------+------------
  bank       | bank_address_key             | UNIQUE          | UNIQUE (address ASC)                               |   true
  bank       | fk_cust_number_ref_customers | FOREIGN KEY     | FOREIGN KEY (cust_number) REFERENCES customers(id) |   true
  bank       | primary                      | PRIMARY KEY     | PRIMARY KEY (id ASC)                               |   true
(3 rows)

Add a column with collation

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> ALTER TABLE bank ADD COLUMN more_names STRING COLLATE en;
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> SHOW COLUMNS FROM bank;
  column_name |     data_type     | is_nullable | column_default | generation_expression |          indices           | is_hidden
--------------+-------------------+-------------+----------------+-----------------------+----------------------------+------------
  id          | INT8              |    false    | NULL           |                       | {primary,bank_address_key} |   false
  balance     | INT8              |    true     | NULL           |                       | {}                         |   false
  payload     | STRING            |    true     | NULL           |                       | {}                         |   false
  active      | BOOL              |    true     | NULL           |                       | {}                         |   false
  location    | STRING            |    true     | NULL           |                       | {}                         |   false
  currency    | STRING            |    true     | NULL           |                       | {}                         |   false
  interest    | DECIMAL           |    false    | 1.3:::DECIMAL  |                       | {}                         |   false
  address     | STRING            |    true     | NULL           |                       | {bank_address_key}         |   false
  cust_number | INT8              |    true     | NULL           |                       | {}                         |   false
  more_names  | STRING COLLATE en |    true     | NULL           |                       | {}                         |   false
(10 rows)

Add a column and assign it to a column family

Add a column and assign it to a new column family

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> ALTER TABLE bank ADD COLUMN location1 STRING CREATE FAMILY f1;
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> SHOW CREATE TABLE bank;
  table_name |                                                          create_statement
-------------+--------------------------------------------------------------------------------------------------------------------------------------
  bank       | CREATE TABLE bank (
             |     id INT8 NOT NULL,
             |     balance INT8 NULL,
             |     payload STRING NULL,
             |     active BOOL NULL,
             |     location STRING NULL,
             |     currency STRING NULL,
             |     interest DECIMAL NOT NULL DEFAULT 1.3:::DECIMAL,
             |     address STRING NULL,
             |     cust_number INT8 NULL,
             |     more_names STRING COLLATE en NULL,
             |     location1 STRING NULL,
             |     CONSTRAINT "primary" PRIMARY KEY (id ASC),
             |     CONSTRAINT fk_cust_number_ref_customers FOREIGN KEY (cust_number) REFERENCES customers(id),
             |     UNIQUE INDEX bank_address_key (address ASC),
             |     FAMILY fam_0_id_balance_payload (id, balance, payload, active, location, currency, interest, address, cust_number, more_names),
             |     FAMILY f1 (location1)
             | )
(1 row)

Add a column and assign it to an existing column family

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> ALTER TABLE bank ADD COLUMN location2 STRING FAMILY f1;
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> SHOW CREATE TABLE bank;
  table_name |                                                          create_statement
-------------+--------------------------------------------------------------------------------------------------------------------------------------
  bank       | CREATE TABLE bank (
             |     id INT8 NOT NULL,
             |     balance INT8 NULL,
             |     payload STRING NULL,
             |     active BOOL NULL,
             |     location STRING NULL,
             |     currency STRING NULL,
             |     interest DECIMAL NOT NULL DEFAULT 1.3:::DECIMAL,
             |     address STRING NULL,
             |     cust_number INT8 NULL,
             |     more_names STRING COLLATE en NULL,
             |     location1 STRING NULL,
             |     location2 STRING NULL,
             |     CONSTRAINT "primary" PRIMARY KEY (id ASC),
             |     CONSTRAINT fk_cust_number_ref_customers FOREIGN KEY (cust_number) REFERENCES customers(id),
             |     UNIQUE INDEX bank_address_key (address ASC),
             |     FAMILY fam_0_id_balance_payload (id, balance, payload, active, location, currency, interest, address, cust_number, more_names),
             |     FAMILY f1 (location1, location2)
             | )
(1 row)

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

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> ALTER TABLE bank ADD COLUMN new_name STRING CREATE IF NOT EXISTS FAMILY f2;
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> SHOW CREATE TABLE bank;
  table_name |                                                          create_statement
-------------+--------------------------------------------------------------------------------------------------------------------------------------
  bank       | CREATE TABLE bank (
             |     id INT8 NOT NULL,
             |     balance INT8 NULL,
             |     payload STRING NULL,
             |     active BOOL NULL,
             |     location STRING NULL,
             |     currency STRING NULL,
             |     interest DECIMAL NOT NULL DEFAULT 1.3:::DECIMAL,
             |     address STRING NULL,
             |     cust_number INT8 NULL,
             |     more_names STRING COLLATE en NULL,
             |     location1 STRING NULL,
             |     location2 STRING NULL,
             |     new_name STRING NULL,
             |     CONSTRAINT "primary" PRIMARY KEY (id ASC),
             |     CONSTRAINT fk_cust_number_ref_customers FOREIGN KEY (cust_number) REFERENCES customers(id),
             |     UNIQUE INDEX bank_address_key (address ASC),
             |     FAMILY fam_0_id_balance_payload (id, balance, payload, active, location, currency, interest, address, cust_number, more_names),
             |     FAMILY f1 (location1, location2),
             |     FAMILY f2 (new_name)
             | )
(1 row)

Add a column with an ON UPDATE expression

New in v21.2: ON UPDATE expressions set the value for a column when other values in a row are updated.

For example, suppose you add a new column to the bank table:

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> ALTER TABLE bank ADD COLUMN last_updated TIMESTAMPTZ DEFAULT now() ON UPDATE now();
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> SELECT id, balance, last_updated FROM bank LIMIT 5;
  id | balance |         last_updated
-----+---------+--------------------------------
   0 |       0 | 2021-10-21 17:03:41.213557+00
   1 |       0 | 2021-10-21 17:03:41.213557+00
   2 |       0 | 2021-10-21 17:03:41.213557+00
   3 |       0 | 2021-10-21 17:03:41.213557+00
   4 |       0 | 2021-10-21 17:03:41.213557+00
(5 rows)

When any value in any row of the bank table is updated, CockroachDB re-evaluates the ON UPDATE expression and updates the last_updated column with the result.

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> UPDATE bank SET balance = 500 WHERE id = 0;
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> SELECT id, balance, last_updated FROM bank LIMIT 5;
  id | balance |         last_updated
-----+---------+--------------------------------
   0 |     500 | 2021-10-21 17:06:42.211261+00
   1 |       0 | 2021-10-21 17:03:41.213557+00
   2 |       0 | 2021-10-21 17:03:41.213557+00
   3 |       0 | 2021-10-21 17:03:41.213557+00
   4 |       0 | 2021-10-21 17:03:41.213557+00
(5 rows)

See also

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