SQL Compare & Diff Checker Online

Compare SQL scripts side by side with text, formatted, and structural diff analysis.

URL fetch uses a server proxy (max 2 MB). SQL comparison still runs locally after load.
Local onlyNo executionStatic analysisPartial AST supportInput total: 159 B

How to Use

  1. Paste or upload the original SQL in the left panel
  2. Paste or upload the modified SQL in the right panel
  3. Select SQL dialect or enable auto-detect
  4. Choose comparison mode and ignore options
  5. Click Compare SQL or enable auto compare
  6. Review summary, side-by-side diff, and structural changes
  7. Export reports or hand off to Validator, Linter, or Explainer

Text diff vs SQL-aware diff

Use Text mode for exact line changes. Use Formatted or Normalizedmode to ignore formatting noise. Use Structural mode to see clause-level changes such as added JOINs, modified WHERE filters, or column list updates.

Example: JOIN added

-- Left
SELECT u.id, u.name FROM users u WHERE u.active = true;

-- Right
SELECT u.id, u.name, o.total
FROM users u
INNER JOIN orders o ON u.id = o.user_id
WHERE u.active = true;

-- Structural summary: JOIN count changed, tables changed

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Frequently Asked Questions

What is an SQL Compare tool?

An SQL Compare tool highlights differences between two SQL scripts or queries. It helps you review changes before deployment, migration, or code review without executing SQL against a database.

How is SQL-aware diff different from plain text diff?

Plain text diff compares characters and lines. SQL-aware diff can normalize formatting, align statements, and detect clause-level changes such as JOIN or WHERE modifications using parser-based structural analysis.

Does this tool execute SQL?

No. It never connects to a database and never runs your queries. Comparison is static analysis only.

Is my SQL uploaded to a server?

No. All comparison runs in your browser. Your SQL stays on your device.

Which comparison modes are available?

Text (raw line diff), Normalized (ignore whitespace/comments/case options), Formatted (beautify both sides then diff), and Structural (statement and clause-level changes via AST parsing).

Can it ignore formatting differences?

Yes. Use Normalized or Formatted mode and enable ignore options such as whitespace, comments, keyword case, and trailing spaces.

Can it compare stored procedures and triggers?

Partially. Complex procedural bodies fall back to text or formatted diff. Clause-level structural diff works best for DML and common DDL such as CREATE TABLE.

Can it compare database schemas?

It compares pasted SQL scripts, including CREATE TABLE blocks. It does not connect to live databases or compare .dacpac files.

Which SQL dialects are supported?

PostgreSQL, MySQL, MariaDB, SQLite, SQL Server (T-SQL), Oracle PL/SQL, BigQuery, Snowflake, Redshift, DuckDB, DB2, Trino, Spark, Hive, ClickHouse, and generic SQL. AST coverage varies by dialect.

Does auto-detect dialect work perfectly?

No. It is heuristic only. Confirm the dialect manually when accuracy matters.

What is the similarity score?

An estimated percentage based on changed vs total lines. It is a heuristic, not proof of semantic equivalence.

Can I export a diff report?

Yes. Download TXT, JSON, unified patch (.patch), HTML, and merged SQL when structural mode produces a merge candidate.

Can I compare SQL dump files?

Yes for reasonably sized dumps pasted or uploaded as .sql files. Very large multi-gigabyte dumps are not practical in-browser.

What is the maximum practical file size?

Small and medium scripts compare instantly. Combined inputs above ~300 KB use a Web Worker. Full highlighting is disabled above ~2M characters; virtualization helps up to roughly ~5 MB.

Does structural mode detect JOIN changes?

Yes for parseable SELECT statements. It reports JOIN count changes, table list changes, and WHERE/GROUP BY/ORDER BY differences.

Are impact notes execution results?

No. Impact notes are static analysis estimates only. They warn about possible cardinality, filter, or breaking changes but do not run queries.

Can I merge SQL changes?

Structural mode can download a best-effort merged script using the right-side version for modified statements. Per-hunk merge is not available in this version.

Can I upload .sql files?

Yes. Upload or drag-and-drop .sql files into either the left (original) or right (modified) panel.

Does it support side-by-side and unified views?

Yes. Switch between side-by-side aligned diff and unified diff in the results panel.

Can I jump to a change in the editor?

Yes. Click a change in the summary list to focus the corresponding line in the left or right editor.

Can I open compared SQL in other tools?

Yes. Hand off to Validator, Linter, Explainer, or open a compare pair from the Formatter original vs formatted output.

Does it work offline?

Yes. After the page loads, comparison works offline because processing is client-side.

What browsers are supported?

Modern Chromium, Firefox, Safari, and Edge with Web Worker and localStorage support.

Is this tool free?

Yes. No account, usage limit, or per-comparison charge.

Can it compare more than two files at once?

Not in this version. Compare one left script against one right script.

Can it compare folder trees or URLs?

Not in this version. Paste or upload SQL text only.

Why use formatted compare before code review?

Formatting-only diffs hide noise so reviewers focus on logic changes such as columns, joins, filters, and limits.

What keyboard shortcut runs compare immediately?

Ctrl+Enter on Windows/Linux or Cmd+Enter on Mac.

Will identical formatting-only SQL show as identical?

In Formatted or Normalized mode with appropriate ignore options, yes. Raw Text mode will still show line differences.

Can I save my comparison?

Your draft is auto-saved in localStorage. Use Save compare pair to store a handoff payload for reloading the same left/right inputs.

Can I compare multiple SQL files?

Yes. Upload multiple .sql files on either side. They are combined with file markers and compared as one script, with removable file chips in the editor toolbar.

Can I load SQL from a URL?

Yes. Paste a public http(s) URL and click Fetch URL. A server proxy retrieves up to 2 MB of text; comparison then runs locally in your browser.

What does Schema (DDL) mode do?

Schema mode compares CREATE TABLE blocks to detect added/removed/modified tables, columns, constraints, and indexes. It also provides migration hint comments for review.

Can I merge changes per statement?

Yes. Open the Merge tab and choose left, right, or both for each aligned statement. Download merged SQL after selecting resolutions.

What does align by object name do?

When enabled, statements are matched by object identity (e.g. CREATE TABLE users) instead of only by position. This improves diff accuracy when statements are reordered.