Compare SQL Online Free — Side-by-Side SQL Query Diff Tool

What is a SQL Compare Tool?

A SQL compare (or SQL diff) tool highlights the differences between two SQL scripts so you can see exactly what changed without squinting between two windows. Paste an original query and a modified version, and the tool lines them up using a longest-common-subsequence algorithm, marking added lines in green, removed lines in red, and modified lines in orange. On modified lines it goes a step further and highlights the individual tokens that changed, so a one-column rename or a changed join condition is obvious at a glance. It is the fastest way to review query edits, track schema changes, or understand what a colleague changed in a shared script. Unlike a plain text diff, a SQL-aware compare keeps the result readable by tokenizing keywords, strings, and identifiers, so the highlighted changes map directly to query semantics rather than raw characters. Because the comparison runs on SQL tokens rather than raw lines, it tolerates harmless reformatting while still surfacing real logic changes.

Compare SQL Queries Online

Comparing SQL queries online beats opening a desktop diff tool when all you need is to see what changed between two versions of a statement. Paste one version into panel A and the other into panel B, then press Compare — the tool lines them up token by token and marks every added, removed and modified element. There is nothing to install, no account to create and no upload: the comparison runs entirely in your browser, which is what makes it practical for production SQL you would rather not paste into a third-party service.

The same workflow covers stored procedures, view definitions and full migration scripts. When you compare a stored procedure between staging and production, or compare two SQL scripts before a release, read the orange modified lines first — that is where behaviour usually changes: a different join type, a dropped filter condition, a renamed column. Whitespace and casing show up as token-level modifications, so re-indented code never hides the one line that actually matters. Very large scripts are easier to review in blocks, or you can run both versions through the SQL formatter first so the diff aligns on structure instead of indentation.

How to Use the Compare Tool

1. Paste the original SQL into the left panel (A) and the modified SQL into the right panel (B).
2. Click Compare, or press Ctrl+Enter in either panel.
3. Read the diff — green + marks added lines, red − marks removed lines, and orange ~ marks modified lines.
4. On modified lines, inspect the inline highlighting to see the exact tokens that changed.
5. Use the stats bar (added / removed / modified / unchanged) to gauge how large the change is, or click Example to load a sample schema diff.

Common Use Cases

• Reviewing pull requests that modify SQL migrations or stored procedures.
• Comparing a query before and after an optimization to confirm only the intended parts changed.
• Auditing schema differences between two versions of a database.
• Verifying that a formatter or linter only reformatted code without changing logic.
• Tracking edits made by teammates to shared reporting queries.
• Comparing database schema exports across environments (dev, staging, production).

Example

Compare two versions of a query — the tool marks the join change, the filter change, and the new column.

Tips

The comparison is case-insensitive on trimmed line text, so formatting-only differences (extra spaces, line breaks) are surfaced as “modified” at the token level — perfect for verifying that a formatter didn't change logic. For large scripts, glance at the stats bar first, then scroll to the orange modified lines where the real logic lives. If two queries look wildly different because of reordering, run both through the SQL Formatter first so the diff aligns on structure rather than whitespace. All processing happens in your browser, so you can safely compare sensitive or proprietary SQL without uploading it anywhere. If the two inputs are very long, paste only the changed region to keep the diff output fast and easy to scan.

Comparing SQL Across Different Dialects

Most comparisons happen between two versions of the same dialect — MySQL against MySQL, PostgreSQL against PostgreSQL. When you compare across dialects (a query written for MySQL that is being ported to PostgreSQL, for example), expect the diff to light up even when the logic is identical: LIMIT versus TOP, IFNULL() versus COALESCE(), backticks versus double quotes around identifiers, and AUTO_INCREMENT versus SERIAL all produce legitimate differences that are not bugs.

A practical workflow when porting a query: format both versions first with the SQL formatter, run the side-by-side compare to isolate the semantic changes, then rewrite the syntax itself with the SQL dialect converter. The dialect-specific formatter pages — MySQL formatter and PostgreSQL formatter — apply the matching keyword sets, so the diff reads as language differences instead of formatting noise. If a comparison shows nothing but whitespace and casing, the rewrite is safe to ship. If it shows a changed join type, a changed predicate or a dropped column, review that line before deploying.

FAQ

How do I compare two SQL queries online?
Paste the original query into panel A and the modified query into panel B, then click Compare or press Ctrl+Enter. Added lines are marked green, removed lines red, and modified lines orange, with the exact changed tokens highlighted inline. No signup and no upload required.

Is this SQL compare tool free?
Yes. The SQL diff tool is completely free — no account, no usage limits, no file-size paywall. The comparison runs entirely in your browser.

Does it work with MySQL, PostgreSQL and SQL Server?
Yes. The comparison is dialect-aware and works with MySQL, PostgreSQL, SQL Server (T-SQL), SQLite, Oracle and other dialects. Identifiers, strings and keywords are tokenized, so a diff on a MySQL query behaves the same way as a diff on a PostgreSQL query.

Can I compare SQL without uploading my queries?
Yes. All comparison happens locally in your browser with JavaScript. Your SQL is never sent to a server, so it is safe to compare proprietary or sensitive queries.

What is the difference between a SQL diff and a text diff?
A plain text diff compares raw characters or lines, so reformatting shows up as a change. A SQL-aware diff tokenizes the query first and highlights the tokens that actually changed, so a change from JOIN to LEFT JOIN is obvious while extra whitespace or casing is ignored.

Can I compare stored procedures and full scripts, not just single queries?
Yes. Anything that is valid SQL text works: a single statement, a view definition, a stored procedure body or an entire migration script. Stored procedure comparisons are the most common case — paste the version from staging and the version from production, and the tool highlights the lines and tokens that differ, including changed WHERE clauses, new columns and renamed variables.

How is this different from Redgate SQL Compare or a desktop diff tool?
Desktop tools such as Redgate SQL Compare connect to two live databases and compare the schema objects themselves, which needs installed software, a licence and database credentials. This tool compares the SQL text in your browser: no install, no signup and no credentials. Use it when you already have the two scripts — a query rewrite, a migration file, a procedure body — and simply want to see the differences.