Streams for change data capture in Snowflake - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a stream on the table 'orders' to capture changes.

Snowflake

CREATE OR REPLACE STREAM orders_stream ON TABLE orders [1] = FALSE;

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

AAPPEND_ONLY

BCHANGE_TRACKING

CALL

DINSERT_ONLY

Attempts:

3 left

💡 Hint

Common Mistakes

Using INSERT_ONLY captures only inserts, missing updates and deletes.

CHANGE_TRACKING is not a valid stream type in Snowflake.

The APPEND_ONLY = FALSE option captures all changes (inserts, updates, deletes) on the table.

2fill in blank

medium

Complete the code to query the stream 'orders_stream' for inserted rows only.

Snowflake

SELECT * FROM orders_stream WHERE [1] = 'INSERT';

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

ACHANGE_TYPE

BMETADATA$ACTION

CACTION_TYPE

DROW_CHANGE

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent column like CHANGE_TYPE.

Confusing the metadata column name.

The METADATA$ACTION column indicates the type of change: 'INSERT', 'UPDATE', or 'DELETE'.

3fill in blank

hard

Fix the error in the stream creation by choosing the correct option for the stream type.

Snowflake

CREATE STREAM customer_stream ON TABLE customers [1] = TRUE;

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

AAPPEND_ONLY

BALL

CCHANGE_TRACKING

DINSERT_ONLY

Attempts:

3 left

💡 Hint

Common Mistakes

Using CHANGE_TRACKING which is not supported.

Using ALL when only inserts are needed.

The APPEND_ONLY = TRUE stream type is valid and captures only inserts. Other options like CHANGE_TRACKING are invalid in Snowflake.

4fill in blank

hard

Fill both blanks to create a stream showing initial rows on the 'products' table.

Snowflake

CREATE OR REPLACE STREAM products_stream ON TABLE products [1] = [2];

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

ASHOW_INITIAL_ROWS

BAPPEND_ONLY

CTRUE

DFALSE

Attempts:

3 left

💡 Hint

Common Mistakes

Using APPEND_ONLY which captures only inserts.

Setting SHOW_INITIAL_ROWS to FALSE excludes initial rows.

The SHOW_INITIAL_ROWS = TRUE option allows the stream to include initial rows of the table in addition to capturing changes.

5fill in blank

hard

Fill all three blanks to query the stream 'inventory_stream' for deleted rows and select the metadata column, the product_id, and quantity.

Snowflake

SELECT [1], product_id, quantity FROM inventory_stream WHERE [2] = 'DELETE' ORDER BY [3];

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

AMETADATA$ACTION

Cproduct_id

Dquantity

Attempts:

3 left

💡 Hint

Common Mistakes

Using different column names for metadata action.

Ordering by quantity instead of product_id.

The METADATA$ACTION column is used to filter for deletes and also selected. Ordering by product_id organizes the output.

Practice

1. What is the main purpose of a stream in Snowflake for change data capture?

easy

A. To automatically delete old data from a table

B. To create a full backup of the table data every hour

C. To track only the changes (inserts, updates, deletes) on a table without copying all data

D. To replicate data to another database in real-time

Solution

1. Step 1: Understand the role of streams

   Streams in Snowflake track changes like inserts, updates, and deletes on a table without copying the entire data.

2. Step 2: Compare options with stream purpose

   Options A, B, and D describe deletion, backup, and replication, which are not the main function of streams.

3. Final Answer:

   To track only the changes (inserts, updates, deletes) on a table without copying all data -> Option C

4. Quick Check:

   Streams track changes = C [OK]

Hint: Streams track only changes, not full data copies [OK]

Common Mistakes:

• Thinking streams copy full table data
• Confusing streams with backups
• Assuming streams delete data automatically

2. Which of the following is the correct syntax to create a stream on a table named orders in Snowflake?

easy

A. CREATE STREAM orders_stream ON TABLE orders;

B. CREATE STREAM orders_stream FOR TABLE orders;

C. CREATE STREAM orders_stream ON orders;

D. CREATE STREAM orders_stream FROM orders;

Solution

1. Step 1: Recall Snowflake stream creation syntax

   The correct syntax uses CREATE STREAM <name> ON TABLE <table_name>.

2. Step 2: Match options with syntax

   CREATE STREAM orders_stream ON TABLE orders; matches the correct syntax exactly. Options B, C, and D use incorrect keywords or omit TABLE.

3. Final Answer:

   CREATE STREAM orders_stream ON TABLE orders; -> Option A

4. Quick Check:

   CREATE STREAM ... ON TABLE ... = A [OK]

Hint: Use ON TABLE keyword when creating streams [OK]

Common Mistakes:

• Omitting ON TABLE keywords
• Using FOR TABLE instead of ON TABLE
• Using FROM instead of ON TABLE

3. Given a stream orders_stream on table orders, what will the following query return?

SELECT * FROM orders_stream;

Assume some rows were inserted and updated since the last query.

medium

A. Only the rows that were inserted or updated since the last query

B. An error because streams cannot be queried directly

C. Only the rows that were deleted from the orders table

D. All rows from the orders table

Solution

1. Step 1: Understand what querying a stream returns

   Querying a stream returns the changed rows (inserts, updates, deletes) since the last time it was queried or consumed.

2. Step 2: Analyze the query behavior

   The query selects all changes from orders_stream, so it returns only inserted or updated rows since last read, not all rows or errors.

3. Final Answer:

   Only the rows that were inserted or updated since the last query -> Option A

4. Quick Check:

   Streams return changed rows = D [OK]

Hint: Streams return only changed rows since last read [OK]

Common Mistakes:

• Thinking streams return full table data
• Assuming streams return deleted rows only
• Believing streams cannot be queried

4. You created a stream on a table but notice it does not capture existing rows as inserts initially. What is the likely cause?

medium

A. The stream was created with the wrong table name

B. Streams only capture changes made to the table after the stream was created

C. Streams do not capture inserts, only updates and deletes

D. The table is empty, so no rows to capture

Solution

1. Step 1: Recall stream behavior for existing rows

   Streams in Snowflake track only DML changes made after the stream is created. Existing rows are not captured as inserts.

2. Step 2: Evaluate other options

   The stream was created with the wrong table name would cause errors, not missing initial rows. Streams do not capture inserts, only updates and deletes is false; streams capture inserts too. The table is empty, so no rows to capture is possible but less likely if table has data.

3. Final Answer:

   Streams only capture changes made to the table after the stream was created -> Option B

4. Quick Check:

   Streams capture post-creation changes only [OK]

Hint: Streams track post-creation changes only [OK]

Common Mistakes:

• Not realizing streams only track post-creation changes
• Assuming streams capture only updates and deletes
• Confusing stream creation errors with missing data

5. You want to process only new and changed rows from a large sales table daily. Which approach using streams is best to minimize resource use and ensure no data is missed?

hard

A. Create a stream and query the full sales table daily

B. Create multiple streams on sales for inserts, updates, and deletes separately

C. Create a stream and never consume it, just query the sales table directly

D. Create a stream on sales and consume the stream daily

Solution

1. Step 1: Understand efficient change capture

   Create a stream to track changes since creation, then consume it daily to process only new changes efficiently.

2. Step 2: Evaluate resource efficiency and correctness

   Consuming the stream daily processes only changes, saving resources. A queries full table daily, wasting resources. C never consumes but queries full table, missing stream benefits. D is unnecessary complexity.

3. Final Answer:

   Create a stream on sales and consume the stream daily -> Option D

4. Quick Check:

   Stream + daily consume = efficient change capture [OK]

Hint: Create stream and consume daily for efficiency [OK]

Common Mistakes:

• Querying full table instead of consuming stream
• Not consuming the stream regularly
• Creating multiple unnecessary streams