power-query

# Power Query for Semantic Models Author, validate, and test Power Query M expressions in semantic model import partitions. Covers writing correct M code, preserving query folding, validating expressions, and testing them by executing against real data sources. ## Partition Expressions Each import table in a semantic model has a partition with an M expression defining what data gets loaded during refresh. The expression typically connects to a data source, navigates to a table/view, and applies transformations. ### Structure of a Partition Expression ``` let Source = Sql.Database(#"SqlEndpoint", #"Database"), Data = Source{[Schema="dbo", Item="Orders"]}[Data], #"Removed Columns" = Table.RemoveColumns(Data, {"InternalId"}), #"Changed Type" = Table.TransformColumnTypes(#"Removed Columns", {{"Amount", Currency.Type}}) in #"Changed Type" ``` Key elements: - **Parameters**: `#"SqlEndpoint"`, `#"Database"` are shared M parameters defined at the model level - **Navigation**: `Source{[Schema="dbo", Item="Orders"]}[Data]` navigates to a specific table - **Steps**: Each step is a named variable in the `let...in` chain - **Quoted identifiers**: Step names with spaces use `#"Step Name"` syntax ### Extracting Expressions ```bash # Get partition expression from TMDL via fab fab get "<Workspace>.Workspace/<Model>.SemanticModel" -f \ -q "definition.parts[?path=='definition/tables/<Table>.tmdl'].payload" # Get shared M parameters fab get "<Workspace>.Workspace/<...