What are SQL database projects?
Applies to: 
SQL Server 2022 (16.x)
Azure SQL Database
Azure SQL Managed Instance
A SQL database project is a local representation of SQL objects that comprise the schema for a single database, such as tables, stored procedures, or functions. The development cycle of a SQL database project enables database development to be integrated into a continuous integration and continuous deployment (CI/CD) workflows familiar as a development best practice.
Overview
SQL projects are based in declarative T-SQL statements. In your SQL database project code, you create each object once. If you need to change something about that object, such as adding columns or changing a data type, you modify the singular file that declares the object for the first and only time.
When a SQL database project is built, the output artifact is a .dacpac file. New and existing databases can be updated to match the contents of the .dacpac by publishing the .dacpac to a target database.
The SQL database projects framework around your database code that adds two foundational capabilities to that set of files with its build process:
- validation of references between objects and the syntax against a specific version of SQL
- deployment of the build artifact to new or existing databases
The functionality for SQL database projects is provided by the Microsoft.SqlServer.DacFx .NET library and is surfaced in several tools for SQL development. DacFx has multiple extensibility points, such as modification of deployment steps and the ability to create custom rules for code analysis. The project SDK for SQL projects is Microsoft.Build.Sql, currently available in preview and advised for new development.
Validation
When a SQL project is built, the relationships between objects are validated. For example, a view definition can't contain a table or columns that don't exist in the SQL project.
Additionally, a SQL project contains a property in its .sqlproj file called the "target platform". This information is used during the build process to validate that the functions and T-SQL syntax exists in that version of SQL. For example, the JSON functions added in SQL Server 2022 can't be used in a SQL project set to the Sql140 (SQL Server 2017) target platform.
To build a SQL project, we run dotnet build from the command line. In graphical tools that support SQL projects (Azure Data Studio, VS Code, and Visual Studio), there's a menu item to build the SQL project.
The console output of the build process might contain errors (build failure) or warnings. Build warnings can include inconsistent casing in object names and other customizable best practices, but don't fail the build.
The artifact output of the build process is a .dacpac file, which can be found for a build with default settings in the bin/Debug folder.
Deployment
The output file, the .dacpac, is powerful, reusable, and declarative artifact. With this file, we can use SqlPackage or other tools to apply our database code to a database. The SqlPackage command to deploy a .dacpac is the publish command.
For example, sqlpackage /Action:Publish /SourceFile:yourfile.dacpac /TargetConnectionString:{yourconnectionstring}.
New databases
SqlPackage navigates the object relationships to create each object in the right order when publishing a dacpac to a new database. For example, SqlPackage creates Table_A before Table_B when Table_B has a foreign key to Table_A.
You don't want to be executing a whole folder of SQL scripts, especially when you could be using SQL projects which automatically executes each T-SQL section in the right order based on object relationships.
Existing databases
In addition to navigating the object hierarchy when publishing to new databases, the .dacpac publish process also calculates the difference between a source .dacpac and a target database before determining what steps it needs to take to update that database. For example, if Table_C is missing two columns in the database that it has in the SQL project and StoredProcedure_A was changed, SqlPackage creates an ALTER TABLE statement and an ALTER PROCEDURE statement instead of blindly trying to create a bunch of objects.
The flexibility provided by the publish command to existing databases isn't limited to a single database. One .dacpac can be deployed multiple times, such as when upgrading a fleet of a hundred databases.
When to use
SQL database projects are a great fit for teams that are looking to integrate database development into a CI/CD workflow. The declarative nature of SQL projects allows for a single source of truth for the database schema, and the build and publish process provides a repeatable and reliable way to deploy changes to databases.
SQL database projects are used to track the source of truth for database state, including development with an object-relational mapper (ORM) such as EF Core. Either a graphical tool or the command line can be used to extract the schema of a database to a SQL project, regardless of the ORM used to create the database.
SQL database projects support the SQL Server and Azure SQL family of databases, including Azure SQL Database and Azure Synapse Analytics. Whether you're developing an application or a data warehouse, SQL database projects can be used to manage the schema of your database. SQL projects can be developed from tools in Visual Studio, VS Code, and Azure Data Studio.
Original projects vs SDK-style projects (preview)
The original SQL project format is based on MSBuild (.NET Framework) and is the format used by SQL Server Data Tools in Visual Studio. The SDK-style project format is based on the new SDK-style projects introduced in .NET Core and is the format used by the SQL Database Projects extension for Azure Data Studio and VS Code. Support for SDK-style SQL projects in Visual Studio is on the roadmap.
New development work should consider using the SDK-style project format, as it's the format that will be supported in the future. The SDK-style project format is more flexible and contains new features not available with the original SQL projects:
- .NET 8 support (cross platform)
- NuGet package references for database references
- Default globbing pattern for .sql files in the project
SDK-style projects have a superset of functionality from original SQL projects and existing SQL projects can be converted to SDK-style projects through modification of the project file. The exception to the functionality coverage is support for SQLCLR objects, which require .NET Framework and aren't supported in SDK-style projects.