Deleting a column from a model table does not delete the column from a partition query definition. If the column you are deleting is part of a partition, you must manually delete the column from the partition query definition. Failure to delete the column from the partition query definition will cause the column to be queried and data returned, but not populated to the model table, during processing operations. For more information, see Partitions (SSAS Tabular).
To delete a model table column
In the model designer, in the table that contains the column you want to delete, right-click on the column, and then click Delete.
To delete a model table column by using the Table Properties dialog box
In the model designer, click on the table which contains the column you want to delete, then click the Table menu, and then click Table Properties.
In Column names from, select Model (to use model table column names, if different from source).
In the Edit Table Properties dialog box, in the table preview window, uncheck the column you want to delete, and then click OK.