How to Change a Column Type in Snowflake
Last updated July 24, 2026 · By the SaturnSQL team
ALTER TABLE ... ALTER COLUMN only allows safe changes (e.g. widening VARCHAR, increasing NUMBER precision). For real type changes, add a new column, backfill it with a cast, then swap names.
Allowed in place
ALTER TABLE orders ALTER COLUMN note SET DATA TYPE VARCHAR(2000);The add-backfill-swap pattern
ALTER TABLE orders ADD COLUMN amount_v2 NUMBER(12,2);
UPDATE orders SET amount_v2 = TRY_CAST(amount AS NUMBER(12,2));
ALTER TABLE orders DROP COLUMN amount;
ALTER TABLE orders RENAME COLUMN amount_v2 TO amount;Run this in SaturnSQL
SaturnSQL is a browser-based SQL editor for teams: shared query library, schema-aware autocomplete, and scheduled exports to Google Sheets and Slack.
Try it free