How to use the SQL ALTER TABLE Generator
1. Enter the table name and choose the SQL dialect.
2. Pick the ALTER TABLE action from the dropdown.
3. Fill in the column details. The correct DDL is generated live — copy and run it.
What is it?
ALTER TABLE modifies an existing table's structure without recreating it. Common operations include adding new columns as requirements evolve, modifying column types to accommodate larger values, dropping obsolete columns, renaming columns for clarity, and managing indexes.
Syntax differs significantly between databases — especially RENAME COLUMN (not supported in older MySQL) and MODIFY vs ALTER COLUMN. This tool generates the correct syntax for MySQL, PostgreSQL, MS SQL Server, and SQLite.
Benefits
Generate INSERT and CREATE TABLE statements instantly
Convert JSON, CSV, or a field list into ready-to-run SQL in seconds — no manual quoting, no counting columns, no copy-paste errors from spreadsheet data.
Build SELECT queries without memorising syntax
The visual query builder constructs WHERE conditions, ORDER BY, LIMIT, and DISTINCT clauses interactively — useful for anyone who writes SQL occasionally rather than daily.
Migrate between MongoDB and relational databases
Convert MongoDB find, insert, update, and delete operations directly to SQL equivalents — speed up data migration planning or schema exploration.
All your data stays in the browser
No SQL query, schema definition, or database content is ever uploaded to a server. Everything runs entirely client-side, making these tools safe to use with sensitive data.
Frequently asked questions
Can I undo an ALTER TABLE?
Not directly — there's no automatic rollback. Always take a backup before running structural changes on production tables. You can reverse the change manually (e.g. DROP COLUMN to undo ADD COLUMN).
What if I need to add multiple columns?
Run the tool multiple times and combine the statements, or use MySQL's multi-column syntax: ALTER TABLE t ADD col1 INT, ADD col2 TEXT;