ALTER TABLE ADD COLUMN keywords

Adds a new column to an existing table.

Syntax#

Flow chart showing the syntax of the ALTER TABLE keyword Flow chart showing the syntax of ALTER TABLE with ADD COLUMN keyword

Description#

Adds a new single column of the specified type. The new column is not back-populated even if the table contains data.

While a single column is added atomically, adding multiple columns is not an atomic operation. QuestDB will stop adding the remaining columns on the list on the first failure. It is therefore possible to add some columns and not others.

info

Adding a new column does not lock the table for reading and does not wait on any reads to finish.

Examples#

Add a new column called comment of type STRING type to the table ratings

New column
ALTER TABLE ratings ADD COLUMN comment STRING

When adding a symbol column, you can also specify symbol related options, for example:

New symbol column
ALTER TABLE ratings ADD COLUMN comment SYMBOL NOCACHE INDEX
tip

For symbol, both nocache and index keywords are optional.

note

For more information on symbol options, please refer to the symbol documentation