Toolxion

SQL Schema Compare – Compare Database Schemas Online

Upload two SQL files to compare database schemas side-by-side. Find missing tables, missing columns, and type mismatches — then generate fix SQL instantly. Everything runs in your browser, nothing is uploaded to a server.

Drop .sql file or click to browse
Drop .sql file or click to browse

What Is SQL Schema Comparison?

SQL schema comparison is the process of analyzing two SQL files side-by-side to find structural differences between database definitions. When working across multiple environments — development, staging, and production — database schemas can quietly drift apart. A column added in development may not exist in production, or a data type may have changed during a migration. These small inconsistencies cause runtime errors, failed queries, and data integrity problems that are hard to debug without a direct comparison.

This free online SQL schema compare tool parses both SQL files entirely in your browser and produces a structured report covering missing tables, missing columns, column type mismatches, and — for full database dumps — missing records. No file is uploaded to any server. Your database schema and data stay private on your device.

What This Tool Checks

  • Missing tables — tables present in one file but absent in the other. For each missing table, a ready-to-run CREATE TABLE statement is generated.
  • Missing columns — columns that exist in one table definition but not the other. An ALTER TABLE ... ADD COLUMN statement is generated for each.
  • Column type differences — same column name but different data types (e.g. VARCHAR(100) vs TEXT). An ALTER TABLE ... MODIFY COLUMN fix is generated.
  • Missing records — for full dump files containing INSERT statements, rows present in one file but not the other are highlighted, matched by primary key or first column value.

How to Generate Fix SQL

After running a comparison, any row in the Tables or Column Differences sections that shows a difference will display a Generate SQL button. Clicking it opens a modal with the exact SQL statement needed to bring File B in line with File A. You can copy it with one click and run it directly in your database client.

  • Missing table in B → full CREATE TABLE with all columns from A.
  • Missing column in B → ALTER TABLE ... ADD COLUMN with the type from A.
  • Missing column in A → ALTER TABLE ... ADD COLUMN with the type from B.
  • Type mismatch → ALTER TABLE ... MODIFY COLUMN to apply A's type to B.

How to Use

  1. Drop or select your first SQL file in the File A box (drag and drop is supported).
  2. Drop or select your second SQL file in the File B box.
  3. Toggle Compare records on or off depending on whether your files are full dumps or schema-only.
  4. Click Compare and review the results.
  5. Click Generate SQL next to any difference to get a ready-to-run fix query.

Common Use Cases

Syncing development and production databases

Export the schema from both environments using mysqldump --no-data or pg_dump --schema-only, then compare the two files here to see exactly what's out of sync before running any migrations.

Reviewing database migrations

Take a schema snapshot before and after running a migration script. Compare the two files to verify the migration applied every intended change and nothing unexpected was altered.

Onboarding to a new project

Compare the project's reference schema SQL against the local database dump to quickly understand what setup steps are missing without reading through long migration histories.

Database backup verification

Compare a backup dump against the live schema to confirm the backup captured the current structure and hasn't fallen behind due to untracked schema changes.

Supported SQL Dialects

This tool parses standard SQL DDL and DML syntax. It works well with exports from:

  • MySQL / MariaDB — mysqldump output, including backtick-quoted identifiers.
  • PostgreSQL — pg_dump schema output with double-quoted identifiers.
  • SQLite — .schema dumps from the SQLite CLI.
  • Generic SQL — any file containing standard CREATE TABLE and INSERT INTO statements.

Stored procedures, triggers, views, and vendor-specific extensions are currently skipped — the tool focuses on table structure and row data.

Frequently Asked Questions

Does this work as a schema compare tool like SSMS Schema Compare?

Yes, for SQL file comparison. SQL Server Management Studio (SSMS) has a built-in Schema Compare feature for connected databases — it connects live to SQL Server instances and can apply changes directly. This tool fills a different gap: it works with exported .sql files from any database (MySQL, PostgreSQL, SQLite, or SQL Server dumps) and runs entirely in your browser without needing a live connection. It is a good choice when you have schema exports but not direct server access.

How does this compare to dbForge Schema Compare?

dbForge Schema Compare is a full desktop tool for SQL Server and MySQL that can compare live database connections and apply changes in one click. This online tool is lighter-weight — it compares exported SQL files in your browser, requires no installation, and is completely free. It is ideal for quick checks, open-source projects, or environments where installing desktop software isn't practical.

Can I compare MySQL or MariaDB database schemas?

Yes. Export schema-only dumps using mysqldump --no-data your_db > schema.sql for each environment, then upload both files here. The tool parses MySQL's backtick-quoted identifiers and standard CREATE TABLE syntax correctly.

Can I compare PostgreSQL database schemas?

Yes. Use pg_dump --schema-only your_db > schema.sql to export a schema-only dump, then compare two exports here. The tool handles double-quoted identifiers and standard PostgreSQL DDL output from pg_dump.

Are my SQL files uploaded anywhere?

No. All parsing and comparison happens entirely in your browser using JavaScript. Your files never leave your device — safe to use with production data, credentials in dumps, or any sensitive schema information.

What happens with large dump files?

Files over 5 MB trigger a warning banner. The comparison will still run, but parsing a very large dump (hundreds of MB) may take several seconds and use significant browser memory. For large files, compare schema-only exports rather than full data dumps.

How are missing records detected?

The tool extracts values from INSERT INTO statements and builds a map keyed by the table's primary key column (detected from PRIMARY KEY declarations) or the first column if no primary key is found. Rows whose key exists in one file but not the other are flagged as missing.

Can I use the generated SQL directly?

Yes — the generated queries are standard SQL. Always review them before running on a production database. The tool generates ALTER TABLE statements without IF NOT EXISTS guards, so running them on a database where the column already exists will produce an error rather than silently overwrite.

Is there a file size limit?

There is no hard limit. The browser will process whatever you load, but very large files (over 50 MB) may cause slowness or run out of browser memory. Splitting large dumps by table before comparing is recommended for extremely large files.