Tasks for scheduling SQL in Snowflake - Step-by-Step Execution

Process Flow - Tasks for scheduling SQL

Create Task

↓

Define SQL Statement

↓

Set Schedule

↓

Enable Task

↓

Task Runs Automatically

↓

Check Task History

↓

Modify or Disable Task

↓

End

This flow shows how to create a scheduled task in Snowflake: create it, define the SQL, set the schedule, enable it, then it runs automatically on schedule.

Execution Sample

Snowflake

CREATE OR REPLACE TASK my_task
  WAREHOUSE = my_wh
  SCHEDULE = 'USING CRON 0 * * * * UTC'
AS
  INSERT INTO my_table VALUES (CURRENT_TIMESTAMP());

ALTER TASK my_task RESUME;

This code creates a task that runs every hour, inserting the current timestamp into a table, then enables the task.

Process Table

Step	Action	SQL Command	Result	Notes
1	Create task with schedule	CREATE OR REPLACE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'USING CRON 0 * * * * UTC' AS INSERT INTO my_table VALUES (CURRENT_TIMESTAMP());	Task 'my_task' created	Task is defined but not running yet
2	Enable task	ALTER TASK my_task RESUME;	Task 'my_task' enabled	Task will run on schedule now
3	Task runs at scheduled time	Automatic execution	Row inserted into my_table	Task runs every hour at minute 0
4	Check task history	SHOW TASK HISTORY LIKE 'my_task';	Shows past runs and status	Verify task success or errors
5	Modify task schedule	ALTER TASK my_task SET SCHEDULE = 'USING CRON 30 * * * * UTC';	Schedule updated	Task now runs at minute 30 each hour
6	Disable task	ALTER TASK my_task SUSPEND;	Task suspended	Task stops running automatically
7	Exit	-	-	Task scheduling complete

💡 Task suspended or deleted, no further automatic runs

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 5	After Step 6
Task State	Not created	Created (suspended)	Enabled (running)	Enabled (running, new schedule)	Suspended (not running)
Schedule	None	Every hour at minute 0	Every hour at minute 0	Every hour at minute 30	Every hour at minute 30

Key Moments - 3 Insights

Why does the task not run immediately after creation?

Because after creation, the task is in a suspended state by default (see Step 1 and Step 2). You must explicitly enable it with ALTER TASK ... RESUME to start automatic runs.

How can I change when the task runs?

You can modify the schedule using ALTER TASK ... SET SCHEDULE (see Step 5). The new schedule takes effect after the command.

What happens if I suspend the task?

Suspending the task stops it from running automatically (see Step 6). It remains defined but inactive until resumed.

Visual Quiz - 3 Questions

Look at the execution table, what is the task state after Step 2?

A Enabled and running

B Suspended

C Created but suspended

D Deleted

💡 Hint

Check the 'Result' and 'Notes' columns for Step 2 in the execution table.

At which step does the task schedule change to run at minute 30 each hour?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look for the ALTER TASK ... SET SCHEDULE command in the execution table.

If you skip Step 2 (enabling the task), what happens?

A Task runs once and stops

B Task runs immediately after creation

C Task never runs automatically

D Task runs only on demand

💡 Hint

Refer to the key moment about task state after creation and enabling.

Concept Snapshot

Snowflake Tasks schedule SQL commands to run automatically.
Create a task with CREATE TASK, define SQL and schedule.
Enable it with ALTER TASK ... RESUME to start running.
Modify schedule with ALTER TASK ... SET SCHEDULE.
Suspend with ALTER TASK ... SUSPEND to stop running.

Full Transcript

This lesson shows how to schedule SQL commands in Snowflake using Tasks. First, you create a task with a SQL statement and a schedule using a cron expression. The task is created but not running until you enable it with ALTER TASK ... RESUME. Once enabled, the task runs automatically on the schedule, for example every hour. You can check the task's run history to see if it succeeded. If needed, you can change the schedule or suspend the task to stop it from running. This process helps automate repetitive SQL operations in Snowflake.

Practice

1. What is the main purpose of a TASK in Snowflake?

easy

A. To create user accounts

B. To store large amounts of data

C. To automate running SQL statements on a schedule

D. To manage network security

Solution

1. Step 1: Understand the role of TASK in Snowflake

   A TASK is designed to run SQL commands automatically at set times.

2. Step 2: Compare TASK purpose with other options

   Storing data, creating users, and managing security are handled by other Snowflake features, not TASKS.

3. Final Answer:

   To automate running SQL statements on a schedule -> Option C

4. Quick Check:

   Task = automate SQL schedule [OK]

Hint: Tasks run SQL automatically on schedule [OK]

Common Mistakes:

• Confusing TASK with data storage
• Thinking TASK creates users
• Assuming TASK manages security

2. Which of the following is the correct syntax to create a simple task that runs every hour in Snowflake?

easy

A. CREATE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'USING CRON 0 * * * * UTC' AS SELECT CURRENT_TIMESTAMP();

B. CREATE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'EVERY 1 HOUR' AS SELECT CURRENT_TIMESTAMP();

C. CREATE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'CRON 0 0 * * *' AS SELECT CURRENT_TIMESTAMP();

D. CREATE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'RUN EVERY HOUR' AS SELECT CURRENT_TIMESTAMP();

Solution

1. Step 1: Identify correct cron syntax for hourly schedule

   The cron expression '0 * * * * UTC' means at minute 0 of every hour in UTC time.

2. Step 2: Check Snowflake task syntax

   Snowflake requires SCHEDULE = 'USING CRON ...' format, so CREATE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'USING CRON 0 * * * * UTC' AS SELECT CURRENT_TIMESTAMP(); matches this correctly.

3. Final Answer:

   CREATE TASK my_task WAREHOUSE = my_wh SCHEDULE = 'USING CRON 0 * * * * UTC' AS SELECT CURRENT_TIMESTAMP(); -> Option A

4. Quick Check:

   Use 'USING CRON' with correct cron string [OK]

Hint: Use 'USING CRON' with proper cron syntax for schedules [OK]

Common Mistakes:

• Omitting 'USING CRON' keyword
• Using invalid cron expressions
• Trying unsupported schedule keywords

3. Given the following task creation:

CREATE TASK daily_task WAREHOUSE = wh1 SCHEDULE = 'USING CRON 0 0 * * * UTC' AS INSERT INTO logs VALUES (CURRENT_TIMESTAMP());

What happens if you do NOT run ALTER TASK daily_task RESUME; after creation?

medium

A. The task runs immediately once and then stops

B. The task runs only when manually triggered

C. The task runs continuously without stopping

D. The task will not run automatically until resumed

Solution

1. Step 1: Understand task state after creation

   By default, a newly created task is in a suspended state and does not run automatically.

2. Step 2: Effect of not resuming the task

   Without running ALTER TASK ... RESUME, the task stays suspended and will not execute on schedule.

3. Final Answer:

   The task will not run automatically until resumed -> Option D

4. Quick Check:

   New tasks are suspended until resumed [OK]

Hint: Always resume tasks after creation to enable scheduling [OK]

Common Mistakes:

• Assuming tasks run immediately after creation
• Thinking tasks run continuously without control
• Believing tasks run only manually by default

4. You wrote this task creation statement:

CREATE TASK my_task WAREHOUSE = wh1 SCHEDULE = 'USING CRON 60 * * * * UTC' AS SELECT 1;

When you try to resume the task, it fails. What is the problem?

medium

A. The warehouse name is missing

B. The cron expression has an invalid minute value

C. The SQL statement is invalid

D. The task name is not allowed

Solution

1. Step 1: Check the cron expression

   Cron minute values must be between 0 and 59. '60' is invalid.

2. Step 2: Validate other parts

   Warehouse is specified, SQL is valid, and task name is allowed, so no issues there.

3. Final Answer:

   The cron expression has an invalid minute value -> Option B

4. Quick Check:

   Cron minutes must be 0-59 [OK]

Hint: Cron minutes must be 0-59, not 60 [OK]

Common Mistakes:

• Using 60 as a minute in cron
• Ignoring cron syntax errors
• Assuming warehouse or SQL errors cause failure

5. You want to create a task that runs a cleanup SQL every day at 3:30 AM UTC and uses warehouse 'clean_wh'. Which of the following is the correct way to create and enable this task?

hard

A. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 30 3 * * * UTC' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME;

B. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'EVERY DAY AT 3:30' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME;

C. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 3 30 * * * UTC' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME;

D. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 30 3 * * *' AS DELETE FROM temp_table;

Solution

1. Step 1: Verify cron expression for 3:30 AM UTC

   The correct cron is '30 3 * * * UTC' meaning minute 30, hour 3.

2. Step 2: Check task creation and enabling

   Task must be created with warehouse, schedule, SQL, and then resumed with ALTER TASK ... RESUME.

3. Step 3: Compare options

   CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 30 3 * * * UTC' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME; uses correct cron, warehouse, SQL, and resumes the task. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'EVERY DAY AT 3:30' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME; uses invalid schedule syntax. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 3 30 * * * UTC' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME; swaps hour and minute. CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 30 3 * * *' AS DELETE FROM temp_table; misses RESUME command.

4. Final Answer:

   CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 30 3 * * * UTC' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME; -> Option A

5. Quick Check:

   Correct cron + resume task = CREATE TASK cleanup_task WAREHOUSE = clean_wh SCHEDULE = 'USING CRON 30 3 * * * UTC' AS DELETE FROM temp_table; ALTER TASK cleanup_task RESUME; [OK]

Hint: Use correct cron and always resume task after creation [OK]

Common Mistakes:

• Swapping hour and minute in cron
• Forgetting to resume the task
• Using unsupported schedule syntax