SQL diff checker
Paste two versions of a query and instantly see what changed. Additions, removals, and unchanged lines are highlighted in a unified diff view — all in your browser, nothing sent to a server.
What is a SQL diff?
A SQL diff compares two versions of a SQL query or schema and highlights exactly what was added, removed, or changed. The concept is the same as git diff but applied specifically to SQL code, making it easy to scan changes without reading both versions end to end.
This is especially useful when queries are long or structurally complex. A diff lets you focus on the meaningful changes — a new join condition, an updated filter, a renamed alias — without getting lost in the parts that stayed the same.
When to use a SQL diff tool
- Reviewing query changes in pull requests before merging
- Auditing database migration files — comparing the old and new versions of a
CREATE TABLE, view, or stored procedure - Debugging regressions — pasting the last working version of a query alongside the current broken one to spot the change
- Documenting how a query or schema evolved over time
- Verifying that an auto-formatter or refactor didn't change query logic
How the diff is computed
The tool uses a standard line-by-line diffing algorithm. Lines present only in the original are marked as removed (red), lines present only in the modified version are marked as added (green), and matching lines appear unchanged. Both sides include line numbers so you can reference specific changes easily.
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FAQ
How does the SQL diff work?
The tool compares your two SQL texts using a line-by-line diffing algorithm. Lines removed from the original are highlighted in red, lines added in the modified version are highlighted in green, and unchanged lines appear on both sides with line numbers for easy reference.
Is my SQL stored or sent to a server?
No. The entire diff runs in your browser using JavaScript. Your SQL is never transmitted, logged, or stored anywhere.
Can I use this for database migration files?
Yes. Paste the before and after versions of a CREATE TABLE, ALTER TABLE, view definition, or stored procedure to quickly see exactly what changed in the migration.
Does it understand SQL semantics?
The diff is text-based, not semantic. It highlights textual differences, not logical equivalence. For example, reordering columns in a SELECT will show as changes even if the query produces the same result. For a semantically clean comparison, format both queries first using the SQL formatter tool, then diff them.
Can I diff non-SQL text with this tool?
Technically yes — the diff algorithm works on any text. But the syntax highlighting is tuned specifically for SQL, so non-SQL content won't get keyword coloring.
Why do I see changes on lines that look the same?
This usually means there are invisible whitespace differences — trailing spaces, tabs vs spaces, or different line endings. Try running both queries through the SQL formatter first to normalize whitespace before comparing.
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