EF Core Migration SQL Explainer

What this tool does

Paste the SQL produced by dotnet ef migrations script and this tool groups every recognizable operation into plain-English categories — tables created or dropped, columns added, altered, or dropped, indexes, foreign keys, and the __EFMigrationsHistory bookkeeping rows EF Core uses to track which migrations have run. Destructive or review-worthy operations — DROP TABLE, DROP COLUMN, ALTER COLUMN, and dropped constraints — are pulled into a warning section at the top so they're the first thing you see before running the script against a real database. It runs entirely in your Blazor Server session using a hand-written statement splitter and pattern matcher — no external SQL parser library, and nothing is sent to a separate API.

How to generate the SQL this tool expects

1. Run dotnet ef migrations script in your project directory to generate the full idempotent SQL for all migrations, or dotnet ef migrations script <FromMigration> <ToMigration> for a specific range.
2. Copy the generated SQL and paste it into the editor on the left.
3. Click Explain (or Ctrl+Enter).
4. Review the destructive-operations warning section first, then the grouped categories below it.

Worked example

This script:

CREATE TABLE [Orders] (
    [Id] int NOT NULL IDENTITY,
    [CustomerId] int NOT NULL,
    [Total] decimal(18,2) NOT NULL,
    CONSTRAINT [PK_Orders] PRIMARY KEY ([Id])
);
GO

ALTER TABLE [Orders] ADD [Status] nvarchar(50) NOT NULL DEFAULT N'Pending';
GO

ALTER TABLE [Orders] ADD CONSTRAINT [FK_Orders_Customers_CustomerId] FOREIGN KEY ([CustomerId]) REFERENCES [Customers] ([Id]) ON DELETE CASCADE;
GO

ALTER TABLE [Orders] DROP COLUMN [LegacyField];
GO

INSERT INTO [__EFMigrationsHistory] ([MigrationId], [ProductVersion])
VALUES (N'20260801120000_AddOrders', N'8.0.10');
GO

produces one destructive warning for Orders.LegacyField being dropped, plus grouped entries under Tables created, Columns added, Foreign keys added, and Migration bookkeeping.

What "destructive or review-worthy" means here

• DROP TABLE and DROP COLUMN — unambiguously destroy data. Always flagged.
• ALTER COLUMN — always flagged, because this script alone doesn't show the column's previous type. A narrower length, a changed precision, or an added NOT NULL can fail or truncate existing data, but that's only visible by comparing against the prior schema — something outside the scope of a single script.
• Dropped constraints — flagged because a constraint name alone doesn't reveal whether it was a foreign key, primary key, or check constraint without the original migration that created it.

What this tool won't do

It does not execute the SQL, connect to a database, or validate that the script will succeed against your actual schema — it's a static classifier of statement shapes, not a SQL engine. It's written primarily against SQL Server's bracketed-identifier syntax (the default provider in most EF Core tutorials and this script's typical output); scripts from other providers with different quoting or DDL syntax will have a higher proportion of statements land in the Unclassified bucket rather than being misclassified with a guess.