How do you add a column or change a table?
Model answer
ALTER TABLE users ADD COLUMN phone VARCHAR(20); Changing types or adding NOT NULL on a large table may lock it or rewrite data, so on live systems add nullable columns first, backfill in batches, then add constraints.
Learn this topic
INSERT, UPDATE and DELETE: Change Data Safely in the course SQL for Beginners: Learn Databases Step by Step.
Sign in to add your own answer.