Dev
Mock Database Migration Generator
Explaining what a database migration looks like is harder when you have to write the SQL from scratch every time you need an example. This generator produces illustrative UP and DOWN migration scripts for five common operations — creating a table, adding a column, adding an index, dropping a column, and renaming a column — across PostgreSQL, MySQL, and SQLite. Each script follows the versioned filename convention (V42__add_status_to_users.sql) and includes both directions so you can show the reversible pattern. Set the table name to whatever entity you are working with, pick the operation that matches the schema change you want to demonstrate, and choose a SQL dialect. PostgreSQL output uses BIGSERIAL and TIMESTAMPTZ; MySQL uses BIGINT AUTO_INCREMENT and DATETIME; SQLite uses INTEGER for the primary key. Column names and types in add-column and related operations are drawn from a realistic pool so each run looks like a real-world migration rather than a toy example. Treat the output as a learning aid and a starting scaffold, not a production migration. Review the SQL carefully, confirm it matches your schema and dialect version, and test it against your database before running anything for real.
How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Enter the exact table name you want to target in the Table Name field (e.g., 'orders' or 'user_profiles').
- Select the migration type from the dropdown — choose create-table, add-column, drop-column, rename-column, or create-index.
- Pick the SQL dialect that matches your database: PostgreSQL, MySQL, or SQLite.
- Click Generate to produce the migration script, then review the UP and DOWN sections for correctness.
- Copy the output and paste it into your migration file, adjusting column types or constraints to match your real schema.
Use Cases
- •Learning how SQL migrations are structured
- •Prototyping a schema change before writing it
- •Illustrating migrations in a tutorial or doc
- •Generating example scripts for a workshop
- •Reminding yourself of common migration patterns
Tips
- →When using create-table, immediately generate a matching create-index script for the same table to scaffold both files at once.
- →For Flyway projects, generate the DOWN script as a separate undo migration file prefixed with U instead of V.
- →SQLite's DROP COLUMN output should be tested against your SQLite version — versions below 3.35.0 require a table-rebuild workaround instead.
- →Use the rename-column operation to generate the syntax reference, then manually add a data migration step if the column holds values that need transforming.
- →MySQL users: the generated scripts assume InnoDB; add ENGINE=InnoDB explicitly if your database defaults to MyISAM to ensure transaction support.
- →Generate the same operation in all three dialects and diff the output to build a personal reference for cross-database syntax differences.
FAQ
what is a database migration
A migration is a versioned script that changes a database schema — creating a table, adding a column, building an index — so the schema can evolve in a controlled, repeatable way across environments. Migrations are run in order, and each is a discrete, reversible step in the database's history.
is the generated migration ready to run in production
No — these scripts are realistic examples for learning and prototyping. The column names and types are randomly chosen from a generic pool, so review the SQL, replace them with your actual schema details, and test against your target database and dialect version before running anything for real.
why use migrations instead of changing the database directly
Migrations record every schema change as code, so the database can be rebuilt identically across development, testing, and production, and changes can be reviewed and rolled back. Editing a database directly loses that history and makes environments drift apart, which migrations exist to prevent.
does the drop-column migration include an automatic rollback script
The DOWN section for a drop-column migration contains a commented-out ALTER TABLE statement with a note that manual restore is required. This reflects real-world practice: once a column is dropped, restoring it without its data requires human judgement about the correct type and any default values.
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