The Tabular Select transform is created when you drag a structure onto the data cube designer canvas from a data connector that supports tabular data (e.g. XML, CSV, SQL Server table-valued functions).
The SQL Select transform is created when a structure is dragged onto the canvas from a data connector that supports relational queries.
The MDX Select transform is created when a SSAS cube is dragged onto the canvas from the Data Connectors structure.
Enter an SQL statement to make a selection from a data connector instead of dragging native structures onto the canvas.
The Stored Procedure Select transform lets you retrieve data using a relational stored procedure.