Querying historical data (AT, BEFORE) in Snowflake - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to query data as it was at a specific time.

Snowflake

SELECT * FROM sales_data AT(TIMESTAMP => [1]);

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

A'2023-01-01 10:00:00'

B'2023-01-01 11:00:00'

C'2023-01-01 12:00:00'

D'2023-01-01 09:00:00'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put the timestamp in quotes.

Using an invalid timestamp format.

The AT(TIMESTAMP =>) clause lets you query the table as it was at a specific timestamp. You need to provide a valid timestamp string.

2fill in blank

medium

Complete the code to query data as it was before a certain time.

Snowflake

SELECT * FROM sales_data BEFORE(TIMESTAMP => [1]);

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

A'2023-01-15 00:00:00'

B'2023-02-01 00:00:00'

C'2023-03-01 00:00:00'

D'2023-01-01 00:00:00'

Attempts:

3 left

💡 Hint

Common Mistakes

Using AT instead of BEFORE.

Not quoting the timestamp.

The BEFORE(TIMESTAMP =>) clause returns data as it was before the given timestamp.

3fill in blank

hard

Fix the error in the query to correctly use the time travel feature.

Snowflake

SELECT * FROM sales_data [1](TIMESTAMP => '2023-01-10 08:00:00');

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

AAS OF

BBEFORE

CAT

DSINCE

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'AS OF' which is not valid syntax.

Using 'SINCE' which is not supported.

The correct syntax to query data at a specific time is AT(TIMESTAMP =>) followed by the timestamp.

4fill in blank

hard

Fill both blanks to query data before a certain timestamp and order by date.

Snowflake

SELECT * FROM sales_data [1](TIMESTAMP => [2]) ORDER BY sale_date;

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

ABEFORE

B'2023-01-20 00:00:00'

C'2023-02-01 00:00:00'

DAS OF

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the keyword and timestamp positions.

Using 'AT' instead of 'BEFORE'.

Use BEFORE(TIMESTAMP =>) followed by the timestamp to get data before that time.

5fill in blank

hard

Fill all three blanks to query data at a specific time, filter by region, and order by amount.

Snowflake

SELECT * FROM sales_data [1](TIMESTAMP => [2]) WHERE region = [3] ORDER BY amount DESC;

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

AAT

B'2023-01-15 12:00:00'

C'North'

D'2023-01-10 09:00:00'

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the region string properly.

Using 'BEFORE' instead of 'AT'.

Use AT(TIMESTAMP =>) with the timestamp, then filter by region with quotes around the string.

Practice

1. What does the AT clause do when querying historical data in Snowflake?

easy

A. Shows data exactly at a specified point in time

B. Shows data after a specified point in time

C. Shows data before a specified point in time

D. Shows the latest data ignoring time

Solution

1. Step 1: Understand the purpose of AT clause

   The AT clause is used to query data as it existed exactly at a specific timestamp.

2. Step 2: Compare with other time clauses

   Unlike BEFORE, which shows data just before a time, AT shows the exact snapshot at that time.

3. Final Answer:

   Shows data exactly at a specified point in time -> Option A

4. Quick Check:

   AT = exact time snapshot [OK]

Hint: Remember: AT means exact time snapshot, not before or after [OK]

Common Mistakes:

• Confusing AT with BEFORE clause
• Thinking AT shows data after the time
• Assuming AT ignores time and shows latest data

2. Which of the following is the correct syntax to query a table named sales as it was exactly at timestamp '2024-01-01 10:00:00' using Snowflake's time travel feature?

easy

A. SELECT * FROM sales AT '2024-01-01 10:00:00';

B. SELECT * FROM sales AT (TIMESTAMP => '2024-01-01 10:00:00'; )

C. SELECT * FROM sales AT (TIMESTAMP => '2024-01-01 10:00:00')

D. SELECT * FROM sales BEFORE (TIMESTAMP => '2024-01-01 10:00:00');

Solution

1. Step 1: Identify correct syntax for AT clause

   Snowflake requires the AT clause with parentheses and the keyword TIMESTAMP => for time travel queries.

2. Step 2: Check syntax details

   SELECT * FROM sales AT (TIMESTAMP => '2024-01-01 10:00:00') correctly uses AT (TIMESTAMP => '2024-01-01 10:00:00') without a trailing semicolon inside the query string.

3. Final Answer:

   SELECT * FROM sales AT (TIMESTAMP => '2024-01-01 10:00:00') -> Option C

4. Quick Check:

   Correct AT syntax = SELECT * FROM sales AT (TIMESTAMP => '2024-01-01 10:00:00') [OK]

Hint: Use AT (TIMESTAMP => 'timestamp') with parentheses for time travel [OK]

Common Mistakes:

• Using BEFORE instead of AT for exact time
• Omitting parentheses around TIMESTAMP clause
• Adding semicolon inside query string causing syntax error

3. Given the table orders with changes over time, what will the following query return?

SELECT COUNT(*) FROM orders BEFORE (TIMESTAMP => '2024-03-01 12:00:00');

medium

A. Count of rows just before '2024-03-01 12:00:00'

B. Count of rows after '2024-03-01 12:00:00'

C. Count of rows exactly at '2024-03-01 12:00:00'

D. Count of all current rows ignoring time

Solution

1. Step 1: Understand BEFORE clause behavior

   The BEFORE clause returns data as it existed just before the specified timestamp.

2. Step 2: Apply to COUNT query

   The query counts rows in orders table as they were immediately before '2024-03-01 12:00:00'.

3. Final Answer:

   Count of rows just before '2024-03-01 12:00:00' -> Option A

4. Quick Check:

   BEFORE = data just before time [OK]

Hint: BEFORE means data snapshot just before the timestamp [OK]

Common Mistakes:

• Confusing BEFORE with AT clause
• Assuming BEFORE returns data after the timestamp
• Thinking BEFORE returns current data

4. You wrote this query but got a syntax error:

SELECT * FROM customers AT TIMESTAMP => '2024-05-01 09:00:00';

What is the likely cause?

medium

A. Table name should be in quotes

B. Missing parentheses around the TIMESTAMP clause

C. Timestamp format is incorrect

D. Using BEFORE instead of AT

Solution

1. Step 1: Check syntax for AT clause

   The AT clause requires parentheses around the TIMESTAMP => '...' part.

2. Step 2: Identify missing parentheses

   The query misses parentheses, causing a syntax error.

3. Final Answer:

   Missing parentheses around the TIMESTAMP clause -> Option B

4. Quick Check:

   AT clause needs parentheses [OK]

Hint: Always wrap TIMESTAMP clause in parentheses after AT [OK]

Common Mistakes:

• Omitting parentheses around TIMESTAMP
• Confusing syntax with BEFORE clause
• Incorrect timestamp format causing error

5. You want to compare the number of rows in the transactions table exactly at '2024-04-15 08:00:00' and just before that time. Which pair of queries correctly achieves this?

hard

A. SELECT COUNT(*) FROM transactions BEFORE (TIMESTAMP => '2024-04-15 08:00:00');SELECT COUNT(*) FROM transactions AT TIMESTAMP => '2024-04-15 08:00:00');

B. SELECT COUNT(*) FROM transactions BEFORE (TIMESTAMP => '2024-04-15 08:00:00');SELECT COUNT(*) FROM transactions AFTER (TIMESTAMP => '2024-04-15 08:00:00');

C. SELECT COUNT(*) FROM transactions AT (TIMESTAMP => '2024-04-15 08:00:00');SELECT COUNT(*) FROM transactions AT (TIMESTAMP => '2024-04-15 07:59:59');

D. SELECT COUNT(*) FROM transactions AT (TIMESTAMP => '2024-04-15 08:00:00');SELECT COUNT(*) FROM transactions BEFORE (TIMESTAMP => '2024-04-15 08:00:00');

Solution

1. Step 1: Identify query for exact time

   Use AT (TIMESTAMP => '2024-04-15 08:00:00') to get data exactly at that timestamp.

2. Step 2: Identify query for just before time

   Use BEFORE (TIMESTAMP => '2024-04-15 08:00:00') to get data just before that timestamp.

3. Step 3: Verify option matches both queries

   SELECT COUNT(*) FROM transactions AT (TIMESTAMP => '2024-04-15 08:00:00');
   SELECT COUNT(*) FROM transactions BEFORE (TIMESTAMP => '2024-04-15 08:00:00'); correctly uses AT and BEFORE clauses as required.

4. Final Answer:

   SELECT COUNT(*) FROM transactions AT (TIMESTAMP => '2024-04-15 08:00:00');
   SELECT COUNT(*) FROM transactions BEFORE (TIMESTAMP => '2024-04-15 08:00:00'); -> Option D

5. Quick Check:

   AT = exact, BEFORE = just before [OK]

Hint: Use AT for exact time, BEFORE for just before time [OK]

Common Mistakes:

• Swapping AT and BEFORE clauses
• Using AFTER which is invalid in Snowflake time travel
• Using two AT queries with different timestamps