ALTER TABLE

Use the ALTER TABLE command to modify the structure of an existing regular table by adding or deleting its columns. Tables defined with connector settings but without a schema registry can be altered.

Syntax

ALTER TABLE table_name alter_option;

alter_option depends on the operation you want to perform on a table.

Adding a new column

alter_option

ADD [ COLUMN ] column_name data_type [ PRIMARY KEY ] [ DEFAULT default_expr ]

note

Columns added by this command cannot be used by any existing materialized views or indexes. You must create new materialized views or indexes to reference it.

Parameter or clause	Description
ADD [ COLUMN ]	COLUMN is optional.
column_name	Specify the name of the column you want to add.
data_type	The data type of the new column.
DEFAULT	The DEFAULT clause allows you to assign a default value to a column. This default value is used when a new row is inserted, and no explicit value is provided for that column. default_expr is any constant value or variable-free expression that does not reference other columns in the current table or involve subqueries. The data type of default_expr must match the data type of the column. If default_expr is impure, such as using a function like now(), all historical data will be filled with the result of the expression evaluated at the time the statement was executed. For future insertions, the default expression will be evaluated at the time of each respective insertion.

Example

-- Add a column named "age" to a table named "employees" with a data type of integer
ALTER TABLE employees ADD age int;

Dropping an existing column

alter_option

DROP [ COLUMN ] [ IF EXISTS ] column_name

note

You cannot drop columns referenced by materialized views or indexes.

Parameter or clause	Description
DROP [ COLUMN ]	COLUMN is optional.
column_name	Specify the column you want to remove.
IF EXISTS	Do not return an error if the specified column does not exist. A notice is issued instead.

Example

-- Remove a column named "fax" from the "employees" table
ALTER TABLE employees DROP fax;