u_wikilabels=> SELECT DISTINCT workset.*
u_wikilabels-> FROM workset
u_wikilabels-> INNER JOIN workset_task ON workset.id = workset_task.workset_id
u_wikilabels-> WHERE workset_task.task_id IN (
u_wikilabels(> SELECT task.id
u_wikilabels(> FROM task
u_wikilabels(> LEFT JOIN label ON task.id = label.task_id
u_wikilabels(> WHERE task.campaign_id = 49
u_wikilabels(> GROUP BY task.id
u_wikilabels(> HAVING COUNT(*) < 2
u_wikilabels(> );
  id  | campaign_id | user_id  |          created           |          expires
------+-------------+----------+----------------------------+----------------------------
 4878 |          49 | 48735543 | 2017-03-23 15:55:51.729714 | 2017-03-24 15:55:51.729714
 4857 |          49 | 48735543 | 2017-03-22 11:11:39.34919  | 2017-03-23 11:11:39.34919
 4895 |          49 | 48735543 | 2017-03-24 14:19:45.67151  | 2017-03-25 14:19:45.67151
 4862 |          49 | 33254570 | 2017-03-22 14:20:40.150585 | 2017-03-23 14:20:40.150585
 4900 |          49 | 48735543 | 2017-03-24 21:44:05.645503 | 2017-03-25 21:44:05.645503
 4880 |          49 | 14371476 | 2017-03-23 19:03:07.519086 | 2017-03-24 19:03:07.519086
 4893 |          49 | 48735543 | 2017-03-24 12:08:17.604573 | 2017-03-25 12:08:17.604573
 4879 |          49 | 48735543 | 2017-03-23 16:16:07.552385 | 2017-03-24 16:16:07.552385
 4884 |          49 | 11365236 | 2017-03-24 09:03:31.660219 | 2017-03-25 09:03:31.660219
 4848 |          49 | 48735543 | 2017-03-21 19:47:58.248849 | 2017-03-22 19:47:58.248849
 4901 |          49 | 48735543 | 2017-03-24 21:48:18.157163 | 2017-03-25 21:48:18.157163
 4852 |          49 |      272 | 2017-03-21 21:30:17.090082 | 2017-03-22 21:30:17.090082
 4888 |          49 | 14053179 | 2017-03-24 09:36:37.833426 | 2017-03-25 09:36:37.833426
 4890 |          49 | 48735543 | 2017-03-24 11:26:55.195244 | 2017-03-25 11:26:55.195244
 4916 |          49 |       91 | 2017-03-26 13:46:31.748017 | 2017-03-27 13:46:31.748017
 4875 |          49 | 48735543 | 2017-03-23 11:25:32.82768  | 2017-03-24 11:25:32.82768
 4886 |          49 |  7205693 | 2017-03-24 09:16:29.848901 | 2017-03-25 09:16:29.848901
 4847 |          49 | 48735543 | 2017-03-21 19:39:59.961605 | 2017-03-22 19:39:59.961605
 4863 |          49 |  8867635 | 2017-03-22 14:56:31.056275 | 2017-03-23 14:56:31.056275
 4898 |          49 | 48735543 | 2017-03-24 15:52:56.118469 | 2017-03-25 15:52:56.118469
 4854 |          49 |   217476 | 2017-03-22 06:59:44.647843 | 2017-03-23 06:59:44.647843
 4845 |          49 |  8133267 | 2017-03-21 17:29:25.350605 | 2017-03-22 17:29:25.350605
 4866 |          49 | 48735543 | 2017-03-22 20:21:01.652061 | 2017-03-23 20:21:01.652061
 4846 |          49 | 30025318 | 2017-03-21 17:30:26.313702 | 2017-03-22 17:30:26.313702
 4887 |          49 | 42275982 | 2017-03-24 09:26:49.674573 | 2017-03-25 09:26:49.674573
 4843 |          49 | 48735543 | 2017-03-21 16:33:51.790735 | 2017-03-22 16:33:51.790735
 4889 |          49 | 48735543 | 2017-03-24 11:09:24.831047 | 2017-03-25 11:09:24.831047
 4850 |          49 | 12230255 | 2017-03-21 20:56:52.294621 | 2017-03-22 20:56:52.294621
 4876 |          49 | 48735543 | 2017-03-23 13:02:32.084104 | 2017-03-24 13:02:32.084104
 4855 |          49 |    36318 | 2017-03-22 07:15:16.546204 | 2017-03-23 07:15:16.546204
 4872 |          49 | 33254570 | 2017-03-22 22:12:29.881089 | 2017-03-23 22:12:29.881089
 4877 |          49 | 48735543 | 2017-03-23 14:02:44.534074 | 2017-03-24 14:02:44.534074
 4858 |          49 | 31562548 | 2017-03-22 11:28:24.664577 | 2017-03-23 11:28:24.664577
 4896 |          49 | 48735543 | 2017-03-24 14:35:09.76165  | 2017-03-25 14:35:09.76165
 4891 |          49 | 48735543 | 2017-03-24 11:31:53.838433 | 2017-03-25 11:31:53.838433
 4892 |          49 | 48735543 | 2017-03-24 11:47:46.333825 | 2017-03-25 11:47:46.333825
(36 rows)