Is converting DuckDB to Microsoft SQL Server free?

Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.

Will my DuckDB data keep its types in Microsoft SQL Server?

Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real Microsoft SQL Server types rather than everything becoming text. The mapping table above shows exactly what you get.

Do you store my file?

No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.

Convert DuckDB to Microsoft SQL Server

Upload a .duckdb or .ddb file and get back a Microsoft SQL Server SQL script you can load straight into your database. Types are preserved rather than flattened to text. Free, no registration, up to 10MB.

1Upload your file

Click to upload or drag and drop

CSV, Excel, SQLite, SQL, DBF (max 10 MB)

2Choose target format

How your data is typed in Microsoft SQL Server

Generated from the converter's own Microsoft SQL Server type mapping — this is what it actually emits, not an example.

Your data	Microsoft SQL Server type
Whole number	BIGINT
Decimal (money)	DECIMAL(10,2)
Floating point	FLOAT
True / false	BIT
Date	DATE
Date and time	DATETIME2
Short text	NVARCHAR(255)
Long text	NVARCHAR(MAX)
Binary data	VARBINARY(MAX)

Working from a .duckdb file

DuckDB keeps an entire analytical database in one file, with real types behind it - decimals that are decimals, and integers wide enough to be worth checking before you move them somewhere narrower.

→Only the main schema is read. Tables created in another schema, or in a second database attached at query time, are not part of the conversion.
→Views in main are read as though they were tables, so a view's rows are materialised into the target rather than skipped.
→HUGEINT is the one type with nowhere to go: no target here has a 128-bit integer, so those columns are carried across as text rather than silently truncated.
→A DuckDB process that was killed leaves a .duckdb.wal sidecar holding everything it had not checkpointed yet. Upload the database on its own and it opens with no error and no tables at all - send the .wal file alongside it, or checkpoint before you copy the database out.

Which SQL Server this runs on

Microsoft SQL Server is the full product name, and it covers a wide range of places to put a database: Express on a laptop, a Developer instance, a Linux container, a managed Azure SQL database. The script was written not to care which of them it lands in.

→There is no CREATE DATABASE, no USE, and no filegroup or collation clause anywhere in the file, so nothing in it can be refused by an edition that forbids those. Which database it populates is decided by your client's connection.
→No schema is named either, so the tables land in the default schema of whichever login runs the script - dbo for most logins. Moving them elsewhere afterwards is an ALTER SCHEMA ... TRANSFER.
→The primary key is emitted as an unnamed constraint, which the server materialises as a clustered index under a name it invents. Nothing else is indexed, so any index the source carried has to be rebuilt by hand.

Reading DuckDB

→Types, primary keys and NOT NULL constraints are read from the database.
→The file is opened read-only, so your upload is never modified or upgraded in place.

Writing Microsoft SQL Server

→String literals carry the N prefix, so non-ASCII text survives whatever collation the database uses.
→Timestamps become DATETIME2. T-SQL’s TIMESTAMP is a row-version counter, not a point in time.
→Identity columns are wrapped in SET IDENTITY_INSERT so explicit key values load.
→Statements are separated with GO in batches.

What you get

A ZIP containing dump.sql, plus a README with the exact command to load it. If anything about your data needed a judgement call, a _warnings.txt explains it.

Load this dump into SQL Server:

  sqlcmd -S HOST -U USER -P PASSWORD -d DATABASE -i dump.sql

Notes:

  - Text columns are NVARCHAR and literals carry the N prefix, so
    non-ASCII data survives regardless of database collation.
  - Timestamps are DATETIME2. T-SQL's TIMESTAMP type is a row
    version, not a point in time.

Questions

Is converting DuckDB to Microsoft SQL Server free?: Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.
Will my DuckDB data keep its types in Microsoft SQL Server?: Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real Microsoft SQL Server types rather than everything becoming text. The mapping table above shows exactly what you get.
Do you store my file?: No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.