An SQL diff tool compares two SQL queries or migration scripts line-by-line and highlights the differences with SQL keyword-aware syntax highlighting. Useful for reviewing database migration changes, comparing stored procedure versions, and auditing query optimizations.
How to Use the SQL Diff Tool
Database query changes need careful review before deployment. The free SQL diff tool compares two SQL queries or migration scripts and highlights every line that changed, with SQL keywords highlighted in the diff output for easier reading.
Step 1: Paste Your SQL Queries
Paste the original SQL into the left panel and the changed SQL into the right panel. The tool works with SELECT queries, INSERT/UPDATE/DELETE statements, DDL statements like CREATE TABLE and ALTER TABLE, stored procedures, views, and any other SQL text. If your SQL is minified, use the SQL Formatter first to add line breaks before comparing.
Step 2: Click Compare
Click the Compare button to run the diff. The tool uses a Myers LCS-based diff algorithm to find the minimal set of line changes. The stats bar shows total lines added, removed, and unchanged at a glance.
Reading SQL Keyword Highlighting
SQL keywords like SELECT, FROM, WHERE, JOIN, and ALTER TABLE appear in purple within the diff output. This makes it easy to distinguish between structural SQL changes (new JOIN clause) versus data changes (different WHERE values).
Side-by-Side vs Unified View
Side-by-side view places the original and changed SQL in parallel columns. Unchanged lines align across both columns, making it easy to see what context surrounds each change. Unified view shows a single column with + and - prefixes, similar to a git diff, which is more compact for queries with many changes.
Common Use Cases
Database engineers use the SQL diff tool to review migration scripts before running them in production. Backend developers use it to compare ORM-generated queries against hand-written optimized versions. DBAs use it to track changes in stored procedures across releases and ensure only intended modifications were made.
FAQ
Is the SQL diff tool free?
Yes, completely free with no account or signup required. All SQL comparison runs in your browser — your queries are never sent to any server.
Is my SQL data private?
Yes. The diff algorithm runs entirely in client-side JavaScript. Your SQL queries, table names, column names, and data are never uploaded or logged anywhere.
What does SQL syntax-aware highlighting mean?
The tool recognizes SQL keywords (SELECT, FROM, WHERE, JOIN, INSERT, UPDATE, DELETE, CREATE, ALTER, DROP, etc.) and highlights them in a distinct color within the diff output. This makes it easier to read changed SQL lines at a glance.
Can I compare stored procedures and DDL statements?
Yes. The SQL diff tool compares any SQL text line-by-line, including stored procedures, views, triggers, CREATE TABLE statements, ALTER TABLE migrations, and DML queries. It shows exactly which lines changed.
What SQL dialects are supported?
The tool works with any SQL dialect including MySQL, PostgreSQL, SQL Server, SQLite, and Oracle since it compares SQL as plain text. SQL keyword highlighting covers the most common keywords across all major dialects.
How do I use this for database migration review?
Paste your old migration SQL in the left panel and the new migration in the right panel. The diff highlights which ALTER TABLE statements, column additions, or index changes are new, making it easy to review before running the migration in production.