CommandBuilder

CommandBuilder is a utility component used in relational data-access libraries to automate the generation of SQL data-modifying commands, such as INSERT, UPDATE, and DELETE, for a data adapter or similar data pipeline. It works by inspecting a provided SELECT command to infer the target table’s structure and then derives the corresponding commands needed to propagate changes made to in-memory data back to the database.

In the common .NET implementation, SqlCommandBuilder (which derives from a base CommandBuilder) demonstrates this approach. When a data adapter is initialized with a SELECT statement and is paired with a CommandBuilder, the builder automatically creates the InsertCommand, UpdateCommand, and DeleteCommand properties on the adapter. After filling a DataTable, you can modify rows and call Update to apply those changes to the database. The generated commands typically rely on the table’s primary key to identify rows and may employ optimistic concurrency by using original values in their WHERE clauses.

Limitations and considerations include: the technique is best suited for simple, single-table SELECTs and may not support complex joins, multi-table updates, or views that do not expose a primary key. It may not handle all data types or scenarios with computed columns, and the generated SQL is not always optimal for performance-sensitive applications. In cases requiring fine-grained control or complex logic, developers may override the generated commands by supplying explicit InsertCommand, UpdateCommand, and DeleteCommand statements.

Overall, CommandBuilder offers a convenience for rapid scaffolding of data-access layers, reducing the need to write repetitive SQL while still enabling manual customization when needed.