database-migration skill (wshobson) for Claude: safe schema changes

• Create-table examples with run and rollback commands

  Shows a Sequelize, a TypeORM and a Prisma migration and the commands to apply or undo them.

  Try: “Write a Prisma migration that adds a status column to users.”

  Runs code · ORM migrations

• Safe add with a default value and a down step

  A migration that adds a required column with a default and removes it on rollback.

  Write · Add a column with a default

• Three steps: add, switch the app, drop

  Adds the new column and copies data, then the app switches over, then a later migration removes the old column.

  Delete · Rename a column without downtime

• Add, copy and cast, drop, rename

  A multi-step approach for large tables that avoids altering the column in place.

  Delete · Change a column type

• Split an address string into columns

  Reads rows, updates each one with the parsed parts, then drops the old column.

  Delete · Transform data

• Wrap the change in a transaction

  Commits on success and rolls back if anything fails.

  Write · Transaction rollback

• Copy the table first, restore on failure

  Creates a backup table, runs the change, checks it, and drops the backup. On failure it drops the table and restores the copy.

  Delete · Checkpoint rollback

• Extra patterns in references/details.md

  A five-phase zero-downtime column swap (add, dual-write, backfill, read from new, drop old) and a Sequelize example that picks MySQL JSON or PostgreSQL JSONB by dialect. It is not a full database-to-database migration guide.

  Read · Blue-green and dialect example

Watch out for

• Migrations here can drop columns and tables

  Several examples remove columns, and the checkpoint rollback drops and recreates the users table. Run them on a copy and back up first. github.com

• The agent may run migration commands

  Approve a migrate or rollback command only after checking which database the connection string points to. github.com