diff --git a/cylc/flow/rundb.py b/cylc/flow/rundb.py
index ade4cfa9b73..7c4f9ea7e0a 100644
--- a/cylc/flow/rundb.py
+++ b/cylc/flow/rundb.py
@@ -235,8 +235,8 @@ class CylcWorkflowDAO:
         TABLE_TASK_JOBS: [
             ["cycle", {"is_primary_key": True}],
             ["name", {"is_primary_key": True}],
-            ["flow_nums"],
             ["submit_num", {"datatype": "INTEGER", "is_primary_key": True}],
+            ["flow_nums"],
             ["is_manual_submit", {"datatype": "INTEGER"}],
             ["try_num", {"datatype": "INTEGER"}],
             ["time_submit"],
diff --git a/cylc/flow/workflow_db_mgr.py b/cylc/flow/workflow_db_mgr.py
index 67faf0b7830..e3da6451b45 100644
--- a/cylc/flow/workflow_db_mgr.py
+++ b/cylc/flow/workflow_db_mgr.py
@@ -741,11 +741,10 @@ def upgrade_pre_810(pri_dao: CylcWorkflowDAO) -> None:
 
         # We can't upgrade if the flow_nums in task_states are not
         # distinct.
-        if (
-            conn.execute(
-                'SELECT DISTINCT flow_nums FROM task_states;').fetchall()
-            != [('[1]',)]
-        ):
+        from cylc.flow.util import deserialise
+        flow_nums = deserialise(conn.execute(
+            'SELECT DISTINCT flow_nums FROM task_states;').fetchall()[0][0])
+        if len(flow_nums) != 1:
             raise CylcError(
                 'Cannot upgrade-restart from 8.0.x to 8.1.0 IF'
                 ' multiple flows have been used.'
diff --git a/tests/flakyfunctional/database/00-simple/schema.out b/tests/flakyfunctional/database/00-simple/schema.out
index 814faac2a59..8ed66a1f2db 100644
--- a/tests/flakyfunctional/database/00-simple/schema.out
+++ b/tests/flakyfunctional/database/00-simple/schema.out
@@ -5,7 +5,7 @@ CREATE TABLE workflow_params(key TEXT, value TEXT, PRIMARY KEY(key));
 CREATE TABLE workflow_template_vars(key TEXT, value TEXT, PRIMARY KEY(key));
 CREATE TABLE task_action_timers(cycle TEXT, name TEXT, ctx_key TEXT, ctx TEXT, delays TEXT, num INTEGER, delay TEXT, timeout TEXT, PRIMARY KEY(cycle, name, ctx_key));
 CREATE TABLE task_events(name TEXT, cycle TEXT, time TEXT, submit_num INTEGER, event TEXT, message TEXT);
-CREATE TABLE task_jobs(cycle TEXT, name TEXT, submit_num INTEGER, is_manual_submit INTEGER, try_num INTEGER, time_submit TEXT, time_submit_exit TEXT, submit_status INTEGER, time_run TEXT, time_run_exit TEXT, run_signal TEXT, run_status INTEGER, platform_name TEXT, job_runner_name TEXT, job_id TEXT, PRIMARY KEY(cycle, name, submit_num));
+CREATE TABLE task_jobs(cycle TEXT, name TEXT, submit_num INTEGER, flow_nums TEXT, is_manual_submit INTEGER, try_num INTEGER, time_submit TEXT, time_submit_exit TEXT, submit_status INTEGER, time_run TEXT, time_run_exit TEXT, run_signal TEXT, run_status INTEGER, platform_name TEXT, job_runner_name TEXT, job_id TEXT, PRIMARY KEY(cycle, name, submit_num));
 CREATE TABLE task_late_flags(cycle TEXT, name TEXT, value INTEGER, PRIMARY KEY(cycle, name));
 CREATE TABLE task_outputs(cycle TEXT, name TEXT, flow_nums TEXT, outputs TEXT, PRIMARY KEY(cycle, name, flow_nums));
 CREATE TABLE task_pool(cycle TEXT, name TEXT, flow_nums TEXT, status TEXT, is_held INTEGER, PRIMARY KEY(cycle, name, flow_nums));
diff --git a/tests/functional/job-submission/01-job-nn-localhost/db.sqlite3 b/tests/functional/job-submission/01-job-nn-localhost/db.sqlite3
index d3d43bdad13..6b2a3515f4f 100644
--- a/tests/functional/job-submission/01-job-nn-localhost/db.sqlite3
+++ b/tests/functional/job-submission/01-job-nn-localhost/db.sqlite3
@@ -13,13 +13,13 @@ INSERT INTO task_action_timers VALUES('1','foo','"poll_timer"','["tuple", [[99,
 INSERT INTO task_action_timers VALUES('1','foo','["try_timers", "submit-retrying"]','null','[]',0,NULL,NULL);
 INSERT INTO task_action_timers VALUES('1','foo','["try_timers", "retrying"]','null','[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]',99,'0.0','1560508824.17287');
 CREATE TABLE task_events(name TEXT, cycle TEXT, time TEXT, submit_num INTEGER, event TEXT, message TEXT);
-CREATE TABLE task_jobs(cycle TEXT, name TEXT, submit_num INTEGER, is_manual_submit INTEGER, try_num INTEGER, time_submit TEXT, time_submit_exit TEXT, submit_status INTEGER, time_run TEXT, time_run_exit TEXT, run_signal TEXT, run_status INTEGER, platform_name TEXT, job_runner_name TEXT, job_id TEXT, PRIMARY KEY(cycle, name, submit_num));
+CREATE TABLE task_jobs(cycle TEXT, name TEXT, submit_num INTEGER, flow_nums TEXT, is_manual_submit INTEGER, try_num INTEGER, time_submit TEXT, time_submit_exit TEXT, submit_status INTEGER, time_run TEXT, time_run_exit TEXT, run_signal TEXT, run_status INTEGER, platform_name TEXT, job_runner_name TEXT, job_id TEXT, PRIMARY KEY(cycle, name, submit_num));
 CREATE TABLE task_late_flags(cycle TEXT, name TEXT, value INTEGER, PRIMARY KEY(cycle, name));
 CREATE TABLE task_outputs(cycle TEXT, name TEXT, flow_nums TEXT, outputs TEXT, PRIMARY KEY(cycle, name, flow_nums));
 CREATE TABLE task_pool(cycle TEXT, name TEXT, flow_nums TEXT, status TEXT, is_held INTEGER, PRIMARY KEY(cycle, name, flow_nums));
-INSERT INTO task_pool VALUES('1','foo','["1", "2"]','waiting', 0);
+INSERT INTO task_pool VALUES('1','foo','["1"]','waiting', 0);
 CREATE TABLE task_states(name TEXT, cycle TEXT, flow_nums TEXT, time_created TEXT, time_updated TEXT, submit_num INTEGER, status TEXT, flow_wait INTEGER, PRIMARY KEY(name, cycle, flow_nums));
-INSERT INTO task_states VALUES('foo','1','["1", "2"]', '2019-06-14T11:30:16+01:00','2019-06-14T11:40:24+01:00',99,'waiting','0');
+INSERT INTO task_states VALUES('foo','1','["1"]', '2019-06-14T11:30:16+01:00','2019-06-14T11:40:24+01:00',99,'waiting','0');
 CREATE TABLE task_prerequisites(cycle TEXT, name TEXT, flow_nums TEXT, prereq_name TEXT, prereq_cycle TEXT, prereq_output TEXT, satisfied TEXT, PRIMARY KEY(cycle, name, flow_nums, prereq_name, prereq_cycle, prereq_output));
 CREATE TABLE task_timeout_timers(cycle TEXT, name TEXT, timeout REAL, PRIMARY KEY(cycle, name));
 CREATE TABLE xtriggers(signature TEXT, results TEXT, PRIMARY KEY(signature));