DROP can be more convenient to use than
SELECT. For example, to increase performance, use
DROP to remove unused columns after running JOIN statements. If you remove an attribute in the unified dataset with
DROP, it is then populated with nulls.
DROP <col1>, <col2>, ...
This statement removes all of the specified columns from the input dataset.
DROP behaves in the following ways:
- It removes a column only if the name you specified exists in the dataset.
- It does not change the ordering of remaining columns.
- If a column to be dropped duplicates another column, a
“<col> is already being dropped”message appears and removes both columns.
DROPis not a reserved word. You can use it as the name of an attribute or a dataset.
Important: Attempting to
tamr_idhas no effect. If you explicitly
origin_entity_idcolumn, you must manually recreate and repopulate it. See Managing Primary Keys.
DROP column_two, column_three, column_four;
Updated about 2 years ago