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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.


ALTER TABLE table_name alter_option;

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

Adding a new column

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

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 clauseDescription
ADD [ COLUMN ]COLUMN is optional.
column_nameSpecify the name of the column you want to add.
data_typeThe data type of the new column.
DEFAULTThe 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.
-- 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

DROP [ COLUMN ] [ IF EXISTS ] column_name

You cannot drop columns referenced by materialized views or indexes.

Parameter or clauseDescription
DROP [ COLUMN ]COLUMN is optional.
column_nameSpecify the column you want to remove.
IF EXISTSDo not return an error if the specified column does not exist. A notice is issued instead.
-- Remove a column named "fax" from the "employees" table
ALTER TABLE employees DROP fax;

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