ALTER TABLE DROP COLUMN

Deletes a column from an existing table.

Dropping columns will also attempt to remove files belonging to the column from all partitions, thus freeing up disk space immediately. If this is not immediately possible on Windows, the file remove operation is postponed until files are released by all threads. The logical drop column will succeed on Windows in presence of active readers.

caution

Use DROP COLUMN with care, as QuestDB cannot recover data from dropped columns! Backup your database to avoid unintended data loss.

Syntax​

Flow chart showing the syntax of the ALTER TABLE keyword

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

Example​

The following example deletes the column called comment from the table ratings

Dropping a column
ALTER TABLE ratings DROP COLUMN movieId;