diff --git a/samples/Autonomous.sql b/samples/Autonomous.sql
index 0f81b0a4..3e792741 100644
--- a/samples/Autonomous.sql
+++ b/samples/Autonomous.sql
@@ -21,6 +21,8 @@ END;
 $$
 LANGUAGE PLPGSQL;
 
+DELETE FROM timetable.chain WHERE chain_name = 'call_proc_every_10s';
+
 WITH
     cte_chain (v_chain_id) AS (
         INSERT INTO timetable.chain (chain_name, run_at, max_instances, live, self_destruct) 
diff --git a/samples/Basic.sql b/samples/Basic.sql
index ef4c830f..88a4b4c9 100644
--- a/samples/Basic.sql
+++ b/samples/Basic.sql
@@ -1,3 +1,5 @@
+DELETE FROM timetable.chain WHERE chain_name = 'notify_every_minute';
+
 SELECT timetable.add_job(
     job_name            => 'notify_every_minute',
     job_schedule        => '* * * * *',
diff --git a/samples/Chain.sql b/samples/Chain.sql
index 03dd78b2..76162e29 100644
--- a/samples/Chain.sql
+++ b/samples/Chain.sql
@@ -10,6 +10,9 @@ DECLARE
     v_task_id          bigint;
     v_chain_id   bigint;
 BEGIN
+    -- Remove existing chain to make this script idempotent
+    DELETE FROM timetable.chain WHERE chain_name = 'chain_operation';
+
     -- In order to implement chain pperation, we will create a table
     CREATE TABLE IF NOT EXISTS timetable.chain_log (
         chain_log BIGSERIAL,
diff --git a/samples/ClientMessages.sql b/samples/ClientMessages.sql
index c83d8627..639addc5 100644
--- a/samples/ClientMessages.sql
+++ b/samples/ClientMessages.sql
@@ -9,6 +9,8 @@ BEGIN
 END; 
 $BODY$;
 
+DELETE FROM timetable.chain WHERE chain_name = 'raise_client_message_every_minute';
+
 SELECT timetable.add_job(
     job_name            => 'raise_client_message_every_minute',
     job_schedule        => '* * * * *',
diff --git a/samples/CronStyle.sql b/samples/CronStyle.sql
index f5418832..060ca001 100644
--- a/samples/CronStyle.sql
+++ b/samples/CronStyle.sql
@@ -17,6 +17,8 @@ CREATE TABLE IF NOT EXISTS timetable.dummy_log (
 -- │ └────────── hour (0 - 23)
 -- └──────────── minute (0 - 59)
 
+DELETE FROM timetable.chain WHERE chain_name = 'cron_insert_every_2h_on_27th';
+
 SELECT timetable.add_job (
     job_name     => 'cron_insert_every_2h_on_27th',
     job_schedule => '40 */2 27 * *',
diff --git a/samples/DelayedRetry.sql b/samples/DelayedRetry.sql
index 95f54977..1f90e833 100644
--- a/samples/DelayedRetry.sql
+++ b/samples/DelayedRetry.sql
@@ -31,6 +31,8 @@ BEGIN
 END
 $$;
 
+DELETE FROM timetable.chain WHERE chain_name = 'retry_on_fail_delayed';
+
 SELECT timetable.add_job(
         job_name            => 'retry_on_fail_delayed',
         job_schedule        => '@every 10 minutes',
@@ -39,8 +41,8 @@ SELECT timetable.add_job(
         job_live            => TRUE,
         job_ignore_errors   => FALSE,
         job_on_error        => $$SELECT retry_chain_on_error(
-            worker_name => 'worker001', 
+            worker_name => 'demo_worker', 
             maximum_retry_count => 3, 
             minimum_retry_timeout => interval '10 seconds', 
             maximum_retry_duration => interval '5 minutes')$$
-    )
\ No newline at end of file
+    );
\ No newline at end of file
diff --git a/samples/ErrorHandling.sql b/samples/ErrorHandling.sql
index 2eefd83f..224fbbf2 100644
--- a/samples/ErrorHandling.sql
+++ b/samples/ErrorHandling.sql
@@ -1,3 +1,5 @@
+DELETE FROM timetable.chain WHERE chain_name = 'fail_with_on_error_notify';
+
 SELECT timetable.add_job(
         job_name            => 'fail_with_on_error_notify',
         job_schedule        => '* * * * *',
@@ -8,4 +10,4 @@ SELECT timetable.add_job(
         job_on_error        => $$SELECT pg_notify('monitoring', 
             format('{"ConfigID": %s, "Message": "Something bad happened"}', 
                 current_setting('pg_timetable.current_chain_id')::bigint))$$
-    )
\ No newline at end of file
+    );
\ No newline at end of file
diff --git a/samples/Exclusive.sql b/samples/Exclusive.sql
index 327c3993..2744eb8d 100644
--- a/samples/Exclusive.sql
+++ b/samples/Exclusive.sql
@@ -8,6 +8,8 @@ BEGIN
 END; 
 $BODY$;
 
+DELETE FROM timetable.chain WHERE chain_name IN ('exclusive_sleep_every_10s', 'exclusive_sleep_after_10s');
+
 SELECT timetable.add_job(
     job_name            => 'exclusive_sleep_every_10s',
     job_schedule        => '@every 10 seconds',
diff --git a/samples/Log.sql b/samples/Log.sql
index 3adff8ae..fdf83939 100644
--- a/samples/Log.sql
+++ b/samples/Log.sql
@@ -1,3 +1,5 @@
+DELETE FROM timetable.chain WHERE chain_name = 'builtin_log_every_minute';
+
 SELECT timetable.add_job(
     job_name            => 'builtin_log_every_minute',
     job_schedule        => NULL, -- same as '* * * * *'
diff --git a/samples/NoOp.sql b/samples/NoOp.sql
index f7826394..16480da2 100644
--- a/samples/NoOp.sql
+++ b/samples/NoOp.sql
@@ -1,3 +1,5 @@
+DELETE FROM timetable.chain WHERE chain_name = 'noop_every_minute';
+
 SELECT timetable.add_job(
     job_name            => 'noop_every_minute',
     job_schedule        => '* * * * *',
diff --git a/samples/SelfDestruct.sql b/samples/SelfDestruct.sql
index cbe8cb2a..bb3f5fb1 100644
--- a/samples/SelfDestruct.sql
+++ b/samples/SelfDestruct.sql
@@ -1,4 +1,4 @@
-CREATE OR REPLACE FUNCTION raise_func(text)
+CREATE OR REPLACE FUNCTION raise_notice_func(text)
   RETURNS void LANGUAGE plpgsql AS
 $BODY$ 
 BEGIN 
@@ -6,10 +6,12 @@ BEGIN
 END; 
 $BODY$;
 
+DELETE FROM timetable.chain WHERE chain_name = 'notify_then_destruct';
+
 SELECT timetable.add_job(
     job_name            => 'notify_then_destruct',
     job_schedule        => '* * * * *',
-    job_command         => 'SELECT raise_func($1)',
+    job_command         => 'SELECT raise_notice_func($1)',
     job_parameters      => '[ "Ahoj from self destruct task" ]' :: jsonb,
     job_kind            => 'SQL'::timetable.command_kind,
     job_live            => TRUE,
diff --git a/samples/Sleep.sql b/samples/Sleep.sql
index 4c6b978f..aaeb2c02 100644
--- a/samples/Sleep.sql
+++ b/samples/Sleep.sql
@@ -1,3 +1,5 @@
+DELETE FROM timetable.chain WHERE chain_name = 'sleep_every_10s';
+
 SELECT timetable.add_job(
     job_name            => 'sleep_every_10s',
     job_schedule        => '@every 10 seconds',