DML Compare — Compare DML Files Online Free
Before a script rewrites ten thousand rows, read its diff. Compare DML files — every changed INSERT, UPDATE, and DELETE highlighted. Free, private, no signup.
How to Compare DML Files Online
DML Compare turns a DML comparison into three quick steps:
- Add the original .dml file into the first input.
- Then load the updated .dml file into the right panel.
- Click Compare and every difference is highlighted instantly.
Tip: before any data script runs, check UPDATE highlights for WHERE-clause changes — that's the line between one row and all rows. Supported in all major browsers — Chrome, Firefox, Edge, or Safari — on Windows, macOS, Linux, and mobile, and no usage limits apply. Unlimited side-by-side diffs are free, with no signup; the line-by-line and unified views come with Premium.
Understanding the DML File Format
DML (Data Manipulation Language) files contain INSERT, UPDATE, and DELETE statements — the scripts that change data rather than structure. Seed files, data migrations, and fix-up scripts are pure DML, and because these statements modify production rows, comparing versions before execution is a direct data-safety control. Because these statements act on live data, DML file comparison is operational safety work: the highlighted edit is precisely the set of rows that will be touched differently this time.
Common Uses of DML Files
Where teams actually use it, day to day:
- DBAs review data scripts against the approved version before release windows.
- Teams diff seed scripts when two environments contain different data.
- Reviewers check UPDATE statements for WHERE-clause changes before approval.
- Engineers verify a data-fix script targets only the intended rows.
- Analysts compare backfill scripts between revisions.
- Auditors keep the highlighted diff as the change record for data modifications.
Side-by-side review of the seed scripts explains most staging-has-different-data mysteries in one look.
Differences Detected in DML Files
The tool provides row-level data diff across script versions: INSERT vs UPDATE comparison when statement strategy changed, DML statement ordering diff (execution order matters for dependent data), bulk data comparison across large INSERT sets, and SQL transaction diff where BEGIN/COMMIT boundaries moved — every changed value and condition highlighted.
Examples of Changes Found in DML Files
Data-script edits the statement-level diff typically catches:
- A seed file where 14 new INSERT rows were added and 2 reference rows had changed values.
- An UPDATE whose SET clause changed from 'price = price * 1.05' to '* 1.08' — a numeric edit with direct financial impact.
- A DELETE statement whose WHERE clause was narrowed from a date range to specific IDs after review.
- A migration where statements were reordered to satisfy a foreign-key dependency — flagged as structural change.
- A cleanup script where DELETE FROM sessions WHERE expired = 1 lost its WHERE clause in an edit — the diff caught a full-table delete before production did.
Why Use FileDiffs for DML Comparison
Before a data script rewrites ten thousand rows, its diff is the only honest preview of which rows it will actually touch. FileDiffs compares INSERT, UPDATE, and DELETE statements in the browser so the dangerous edits surface first. The page is built for operational safety, not a bare differ, with examples like a session-cleanup DELETE losing its WHERE clause in an edit, the diff catching a full-table delete before production does, exactly the moment this comparison exists for.
Frequently Asked Questions About Compare DML Files Online
Upload both scripts and the tool highlights every changed INSERT, UPDATE, and DELETE statement, including value-level differences within rows. Statement-level highlights show precisely which rows will be touched differently this time.
DDL defines structure (tables, columns); DML changes data (rows). DDL diffs reveal schema changes, while DML diffs reveal exactly which data operations changed between script versions. Use DDL comparison for structure (CREATE, ALTER) and this tool for data scripts (INSERT, UPDATE, DELETE).
Compare the script versions; changed values, added rows, and modified WHERE/SET clauses are word-highlighted — the precise edits that determine what data changes. An UPDATE whose WHERE clause changed is the difference between fixing one row and rewriting them all.
Diff the migration against its previous or approved version before execution; the report is your pre-run safety check on scope and values. Diff the seed scripts of two environments — it explains most staging-has-different-data mysteries in one look.
Keep approved script versions and compare anything executed against them — differences document exactly what data operations diverged from the approved plan. Keep the highlighted comparison as the audit record; it documents intent better than a ticket description.
Yes. Your INSERT, UPDATE, and DELETE scripts are processed locally in the browser, so sensitive data operations never leave your device. Nothing is retained after you close the tab. The files exist only in your browser's memory during the comparison.