SQL Data Comparer

Compare row-level data between two SQL Server, PostgreSQL, or MySQL databases, or between folders of INSERT scripts. Use the WPF desktop app, the CLI, or a bundled MCP server so tools like Cursor and Claude Desktop can enumerate tables, inspect rows and FKs, diff tables, and apply syncs. Reports: JSON, HTML, CSV, JUnit-style XML.

This repo includes a first-party MCP host (SqlDataCompare.Mcp)—no separate package. The CLI supports compare-only (default) or --copy-differences to push inserts/updates/deletes to the destination after a successful compare.

Repository: github.com/felenko/SQL-Data-Comparer

Solution layout

Project	Role
SqlDataCompare.Core	Compare engine, sync, schema, project model, MCP helpers
SqlDataCompare.Wpf	Windows UI (net8.0-windows)
SqlDataCompare.Cli	Command-line compare and optional sync
SqlDataCompare.Mcp	MCP stdio server exposing Core as tools
SqlDataCompare.Tests	Unit tests
SqlDataCompare.Mcp.IntegrationTests	MCP-related checks (see below)

Requirements

• .NET 8 SDK
• WPF UI: Windows (net8.0-windows)

Build

dotnet build SqlDataCompare.sln

Run tests

dotnet test SqlDataCompare.Tests/SqlDataCompare.Tests.csproj

MCP integration tests (SqlDataCompare.Mcp.IntegrationTests):

dotnet test SqlDataCompare.Mcp.IntegrationTests/SqlDataCompare.Mcp.IntegrationTests.csproj

• Always runs source-level checks that SqlDataCompareMcpTools.cs still defines five [McpServerTool] methods (no dependency on the MCP exe, so this project builds even while SqlDataCompare.Mcp is running).
• SQL-backed tests run only when you set SDC_MCP_INTEGRATION_SQL to a SQL Server ADO.NET connection string (any database with at least one table that has a resolvable primary key). If unset, those tests are skipped so CI stays green without secrets.

Example (PowerShell, session only):

$env:SDC_MCP_INTEGRATION_SQL = 'Data Source=localhost\sqlexpress;Initial Catalog=YourDb;User ID=...;Password=...;Encrypt=True;Trust Server Certificate=True'
dotnet test SqlDataCompare.Mcp.IntegrationTests/SqlDataCompare.Mcp.IntegrationTests.csproj

MCP server (stdio)

The server uses the C# MCP SDK (ModelContextProtocol on NuGet). Run:

dotnet run --project SqlDataCompare.Mcp/SqlDataCompare.Mcp.csproj

Tools (exact names may be prefixed by the SDK; check your client’s tool list):

Tool	Purpose
SqlEnumerateTables	List tables (schema, name, display) for a connection.
SqlGetTableDataWithRelations	Read up to N rows (all columns) plus incoming/outgoing foreign keys for that table.
SqlCompareTwoTables	Compare one source table to one destination; JSON includes value diffs and samples.
SqlCopySelectedRowsToDestination	Sync specific rows (JSON array of key objects); set rowOperationKind and insertMissing / updateChanged / deleteExtra. Writes destination only.
SqlCopyProjectDifferencesToDestination	Sync all differences for every table from a full compare project JSON (same shape as a saved .json project, including polymorphic "kind": "database" on endpoints). Full merge per table—not limited to compare sample rows. Writes destination only.

Cursor example (adjust the path):

"sql-data-compare": {
  "command": "dotnet",
  "args": ["run", "--project", "C:/Source/Claude/SqlDataCompare/SqlDataCompare.Mcp/SqlDataCompare.Mcp.csproj"]
}

Treat connection strings and project JSON with embedded secrets as sensitive. Prefer environment variables or client-injected config, not committed files.

Desktop app (Windows)

dotnet run --project SqlDataCompare.Wpf/SqlDataCompare.Wpf.csproj

Load or create a compare project, run compare, review results, then optionally sync selected tables to the destination database.

Command line

dotnet run --project SqlDataCompare.Cli/SqlDataCompare.Cli.csproj -- --project path/to/project.json

Use --help or -h for the built-in usage text.

Compare-only (default) — Reports differences; does not modify any database.

--copy-differences — After compare succeeds (no per-table Error), runs the same style of sync as the app: insert missing rows, update changed values, and optionally delete extra rows on the destination. Applies to all tables in the project worklist (not row-by-row selection). Requires a database destination in the project. If compare reports all tables identical, sync is skipped (no full scan for writes).

Options

Option	Description
--project <path>	Compare project JSON (required).
--report <path>	Full compare results as JSON.
--export-html <path>	HTML report.
--export-csv <path>	CSV summary.
--export-junit <path>	JUnit-style XML.
--copy-differences	Sync to destination after successful compare (see above).
--sync-report <path>	Write sync results JSON (requires --copy-differences).
--sync-delete-extra	Allow DELETE on destination for keys not on source (default: off).
--sync-no-insert-missing	Do not INSERT missing rows.
--sync-no-update-changed	Do not UPDATE changed rows.
--disable-fk-checks	Temporarily relax FK checks on the destination during sync.
--verbosity / -v	e.g. Information, Debug, Trace.

Exit codes

Code	Meaning
0	Compare succeeded and, if --copy-differences was used, sync finished with no sync errors (or sync skipped because everything was identical).
1	Failure: bad project, connection error, compare error on a table, or sync error.
2	Compare-only: at least one table differs (not used when you pass --copy-differences and sync completes successfully).

Example — compare with reports

dotnet run --project SqlDataCompare.Cli/SqlDataCompare.Cli.csproj -- ^
  --project MyProject.json ^
  --report out/compare.json ^
  --export-html out/report.html ^
  -v Information

Example — compare then copy differences

dotnet run --project SqlDataCompare.Cli/SqlDataCompare.Cli.csproj -- ^
  --project MyProject.json ^
  --copy-differences ^
  --sync-report out/sync.json ^
  -v Information

On PowerShell, use a backtick ` for line continuation instead of ^.

Project file (JSON)

Projects describe endpoints (database or insert folder), provider (sqlserver, postgresql, mysql), connection strings or paths, compare options, optional tablesToCompare, and tableOverrides.

Copy the sample and edit for your environment:

copy VisualCasino.example.json MyProject.json

Do not commit real connection strings. Keep secrets local; this repo’s .gitignore excludes VisualCasino.json. Use placeholders or CI-specific files.

See samples/folder-to-folder.sample.json for folder-based endpoints.

Compare performance (troubleshooting)

Tables run in schema/name order. Slow stretches usually mean the next table is large or remote.

At Information verbosity, logs include per-table Loaded … in N ms and merge M ms. Source and destination row reads run in parallel; merge skips redundant sorting when SQL already returns rows ordered by key.

For heavy tables: use tableOverrides with maxRows for a sampled compare, or restrict tablesToCompare.

License

This project is licensed under the MIT License — see LICENSE.