The Tabular Select transform is created when you drag a structure onto the data cube canvas from a data connector that supports tabular data (e.g., Excel, XML, 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 cube from an OLAP database connector is dragged onto the canvas.
Enter a SQL or MDX 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.