Task trees and dependencies in Snowflake - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a task that runs every hour.

Snowflake

CREATE OR REPLACE TASK hourly_task
  WAREHOUSE = my_warehouse
  SCHEDULE = '[1]'
AS
  CALL my_procedure();

Drag options to blanks, or click blank then click option'

A'1 DAY'

B'1 MINUTE'

C'1 WEEK'

D'1 HOUR'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '1 MINUTE' runs the task too frequently.

Using '1 DAY' or '1 WEEK' runs the task less often than required.

The schedule '1 HOUR' makes the task run every hour.

2fill in blank

medium

Complete the code to set a task dependency on another task.

Snowflake

CREATE OR REPLACE TASK dependent_task
  WAREHOUSE = my_warehouse
  AFTER [1]
AS
  CALL another_procedure();

Drag options to blanks, or click blank then click option'

Amy_procedure

Bnon_existing_task

Chourly_task

Dmy_warehouse

Attempts:

3 left

💡 Hint

Common Mistakes

Using a procedure name instead of a task name.

Using a warehouse name instead of a task name.

The AFTER clause specifies the task that must complete before this one runs. 'hourly_task' is the correct dependency.

3fill in blank

hard

Fix the error in the task creation by completing the missing clause.

Snowflake

CREATE OR REPLACE TASK my_task
  WAREHOUSE = my_warehouse
  [1]
AS
  CALL my_procedure();

Drag options to blanks, or click blank then click option'

AWHEN SYSTEM$STREAM_HAS_DATA('my_stream')

BSCHEDULE = '1 DAY'

CRUN ONCE

DAFTER my_task

Attempts:

3 left

💡 Hint

Common Mistakes

Using AFTER with the same task name causes a circular dependency.

RUN ONCE is not a valid clause in Snowflake task creation.

The WHEN clause requires a SCHEDULE or AFTER clause and does not fix the missing requirement alone.

The SCHEDULE clause is required for standalone tasks without an AFTER clause. '1 DAY' schedules the task to run daily.

4fill in blank

hard

Fill both blanks to create a task tree where task_b runs after task_a and task_c runs after task_b.

Snowflake

CREATE OR REPLACE TASK task_b
  WAREHOUSE = my_warehouse
  AFTER [1]
AS
  CALL procedure_b();

CREATE OR REPLACE TASK task_c
  WAREHOUSE = my_warehouse
  AFTER [2]
AS
  CALL procedure_c();

Drag options to blanks, or click blank then click option'

Atask_a

Btask_c

Ctask_b

Dtask_a_procedure

Attempts:

3 left

💡 Hint

Common Mistakes

Using procedure names instead of task names in AFTER clauses.

Creating circular dependencies by referencing tasks incorrectly.

task_b depends on task_a, and task_c depends on task_b, forming a chain.

5fill in blank

hard

Fill all three blanks to create a task that runs every day, depends on task_x, and calls the correct procedure.

Snowflake

CREATE OR REPLACE TASK daily_task
  WAREHOUSE = [1]
  SCHEDULE = [2]
  AFTER [3]
AS
  CALL daily_procedure();

Drag options to blanks, or click blank then click option'

Amy_warehouse

B'1 DAY'

Ctask_x

Ddaily_procedure

Attempts:

3 left

💡 Hint

Common Mistakes

Using procedure name in AFTER clause instead of task name.

Incorrect schedule format.

The warehouse is 'my_warehouse', schedule is '1 DAY' for daily runs, and the task depends on 'task_x'.

Practice

1. What is the main purpose of creating a task tree in Snowflake?

easy

A. To organize tasks so they run in a specific order using dependencies

B. To store data in a hierarchical format

C. To create multiple independent tasks that run simultaneously

D. To backup data automatically

Solution

1. Step 1: Understand task trees concept

   Task trees are used to organize tasks so they run one after another based on dependencies.

2. Step 2: Compare options

   Only To organize tasks so they run in a specific order using dependencies describes organizing tasks with dependencies. Others describe unrelated concepts.

3. Final Answer:

   To organize tasks so they run in a specific order using dependencies -> Option A

4. Quick Check:

   Task trees = ordered tasks [OK]

Hint: Task trees control task order using dependencies [OK]

Common Mistakes:

• Confusing task trees with data storage
• Thinking tasks run independently without order
• Assuming task trees backup data

2. Which Snowflake command correctly sets a task to run after another task named task_A?

easy

A. ALTER TASK task_B SET BEFORE = task_A;

B. CREATE TASK task_B AFTER task_A;

C. ALTER TASK task_B SET AFTER = task_A;

D. ALTER TASK task_A SET AFTER = task_B;

Solution

1. Step 1: Recall syntax for setting dependencies

   Snowflake uses ALTER TASK task_name SET AFTER = other_task; to set dependencies.

2. Step 2: Check each option

   Only ALTER TASK task_B SET AFTER = task_A; matches correct syntax. The option using BEFORE has an invalid keyword. The CREATE TASK option uses AFTER incorrectly. The option altering task_A reverses dependency.

3. Final Answer:

   ALTER TASK task_B SET AFTER = task_A; -> Option C

4. Quick Check:

   SET AFTER syntax = ALTER TASK task_B SET AFTER = task_A; [OK]

Hint: Use ALTER TASK ... SET AFTER = task_name to link tasks [OK]

Common Mistakes:

• Using BEFORE instead of AFTER
• Trying to set dependency during CREATE TASK
• Reversing task order in dependency

3. Given the following tasks and dependencies:

CREATE TASK task_A WAREHOUSE = wh1 AS SELECT 1;
CREATE TASK task_B WAREHOUSE = wh1 AS SELECT 2;
CREATE TASK task_C WAREHOUSE = wh1 AS SELECT 3;
ALTER TASK task_B SET AFTER = task_A;
ALTER TASK task_C SET AFTER = task_B;

If you start task_A, which task runs last?

medium

A. task_A

B. task_B

C. All run simultaneously

D. task_C

Solution

1. Step 1: Analyze task dependencies

   task_B runs after task_A, and task_C runs after task_B, so order is task_A -> task_B -> task_C.

2. Step 2: Identify last task in sequence

   Since task_C depends on task_B, which depends on task_A, task_C runs last.

3. Final Answer:

   task_C -> Option D

4. Quick Check:

   Dependency chain ends with task_C [OK]

Hint: Follow AFTER links to find last task [OK]

Common Mistakes:

• Thinking tasks run in parallel
• Choosing the first task as last
• Ignoring dependency order

4. You have two tasks: task_X and task_Y. You want task_Y to run after task_X. Which command fixes this if task_Y currently runs before task_X?

medium

A. CREATE TASK task_Y SET AFTER = task_X;

B. ALTER TASK task_Y SET AFTER = task_X;

C. ALTER TASK task_Y SET BEFORE = task_X;

D. ALTER TASK task_X SET AFTER = task_Y;

Solution

1. Step 1: Identify correct command to set dependency

   To make task_Y run after task_X, use ALTER TASK task_Y SET AFTER = task_X;.

2. Step 2: Check incorrect options

   ALTER TASK task_X SET AFTER = task_Y; reverses order. ALTER TASK task_Y SET BEFORE = task_X; uses invalid BEFORE keyword. CREATE TASK task_Y SET AFTER = task_X; uses CREATE incorrectly.

3. Final Answer:

   ALTER TASK task_Y SET AFTER = task_X; -> Option B

4. Quick Check:

   SET AFTER fixes order [OK]

Hint: Use ALTER TASK task_Y SET AFTER = task_X to fix order [OK]

Common Mistakes:

• Using BEFORE keyword which is invalid
• Setting dependency on wrong task
• Trying to fix order with CREATE TASK

5. You have a task tree where task_1 runs first, then task_2 and task_3 run after task_1 in parallel, and finally task_4 runs after both task_2 and task_3. How do you configure task_4 to run only after both tasks finish?

hard

A. ALTER TASK task_4 SET AFTER = task_2, task_3;

B. ALTER TASK task_4 SET AFTER = task_2; ALTER TASK task_4 SET AFTER = task_3;

C. ALTER TASK task_4 SET AFTER = task_2 AND task_3;

D. ALTER TASK task_4 SET AFTER = task_2; ALTER TASK task_3 SET AFTER = task_4;

Solution

1. Step 1: Understand multiple dependencies syntax

   Snowflake allows setting multiple tasks in AFTER clause separated by commas to require all to finish.

2. Step 2: Evaluate options

   ALTER TASK task_4 SET AFTER = task_2, task_3; correctly sets task_4 to run after both task_2 and task_3. ALTER TASK task_4 SET AFTER = task_2; ALTER TASK task_4 SET AFTER = task_3; overwrites AFTER twice, only last applies. ALTER TASK task_4 SET AFTER = task_2 AND task_3; uses invalid AND keyword. ALTER TASK task_4 SET AFTER = task_2; ALTER TASK task_3 SET AFTER = task_4; reverses dependency.

3. Final Answer:

   ALTER TASK task_4 SET AFTER = task_2, task_3; -> Option A

4. Quick Check:

   Multiple AFTER tasks separated by commas [OK]

Hint: Use commas to list multiple tasks in SET AFTER [OK]

Common Mistakes:

• Using multiple SET AFTER commands overwriting each other
• Using AND instead of comma
• Setting wrong dependency direction