DATEDIFF and TIMESTAMPDIFF in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find the number of days between two dates.

MySQL

SELECT DATEDIFF([1], '2024-01-01') AS days_difference;

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

A'2024-01-10'

B'2023-12-31'

C'2024-02-01'

D'2024-01-01'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the earlier date as the first argument results in a negative number.

Forgetting to put dates in quotes.

The DATEDIFF function returns the number of days between two dates. Here, the first date should be later than the second to get a positive difference.

2fill in blank

medium

Complete the code to find the number of months between two dates using TIMESTAMPDIFF.

MySQL

SELECT TIMESTAMPDIFF([1], '2023-01-01', '2024-01-01') AS months_difference;

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

ADAY

BYEAR

CMONTH

DHOUR

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'DAY' instead of 'MONTH' returns days, not months.

Using lowercase units which may cause errors.

TIMESTAMPDIFF calculates the difference between two dates in the specified unit. Here, MONTH returns the number of full months between the dates.

3fill in blank

hard

Fix the error in the code to correctly calculate the difference in hours between two timestamps.

MySQL

SELECT TIMESTAMPDIFF([1], '2024-01-01 08:00:00', '2024-01-01 12:00:00') AS hours_difference;

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

ADAY

BMINUTE

CSECOND

DHOUR

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'MINUTE' returns minutes, not hours.

Using 'DAY' returns days, which is too large for this difference.

The unit HOUR correctly calculates the difference in hours between two timestamps.

4fill in blank

hard

Fill both blanks to calculate the number of years and days between two dates.

MySQL

SELECT TIMESTAMPDIFF([1], '2000-01-01', '2024-01-01') AS years_diff, DATEDIFF('2024-01-01', [2]) AS days_diff;

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

AYEAR

B'2000-01-01'

C'2023-12-31'

DMONTH

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'MONTH' instead of 'YEAR' for years difference.

Swapping dates in DATEDIFF causing negative results.

The first blank uses YEAR to get full years difference. The second blank uses the start date '2000-01-01' to calculate days difference from the end date.

5fill in blank

hard

Fill all three blanks to calculate the difference in days, months, and years between two dates.

MySQL

SELECT DATEDIFF([1], [2]) AS days_diff, TIMESTAMPDIFF([3], [2], [1]) AS months_diff, TIMESTAMPDIFF(YEAR, [2], [1]) AS years_diff;

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

A'2024-12-31'

B'2023-01-01'

CMONTH

DDAY

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping dates causing negative differences.

Using wrong units like 'DAY' for months difference.

The first two blanks are dates: the later date first, then the earlier date. The third blank is the unit 'MONTH' for months difference.

Practice

1. What does the MySQL function DATEDIFF(date1, date2) return?

easy

A. The number of days between date1 and date2

B. The number of seconds between date1 and date2

C. The difference in months between date1 and date2

D. The current date and time

Solution

1. Step 1: Understand the function purpose

   DATEDIFF calculates the difference between two dates in days only.

2. Step 2: Confirm the output type

   The output is an integer representing how many days separate the two dates.

3. Final Answer:

   The number of days between date1 and date2 -> Option A

4. Quick Check:

   DATEDIFF returns days difference [OK]

Hint: DATEDIFF always returns days difference between two dates [OK]

Common Mistakes:

• Thinking it returns seconds or months
• Confusing order of dates for output sign
• Using it to get current date/time

2. Which of the following is the correct syntax to find the difference in hours between two datetime values start_time and end_time using TIMESTAMPDIFF?

easy

A. TIMESTAMPDIFF(HOUR, start_time, end_time)

B. TIMESTAMPDIFF(start_time, end_time, HOUR)

C. TIMESTAMPDIFF('HOUR', end_time, start_time)

D. TIMESTAMPDIFF(end_time, start_time, 'HOUR')

Solution

1. Step 1: Recall TIMESTAMPDIFF syntax

   The correct syntax is TIMESTAMPDIFF(unit, datetime1, datetime2) where unit is a keyword like HOUR without quotes.

2. Step 2: Match parameters order

   Unit first, then start_time, then end_time is correct.

3. Final Answer:

   TIMESTAMPDIFF(HOUR, start_time, end_time) -> Option A

4. Quick Check:

   Unit first, then start, then end [OK]

Hint: TIMESTAMPDIFF(unit, start, end) with unit unquoted [OK]

Common Mistakes:

• Putting unit last or in quotes
• Swapping start and end parameters
• Using lowercase unit in quotes

3. Given the query:
SELECT TIMESTAMPDIFF(DAY, '2024-01-01', '2024-01-10') AS diff_days;
What will be the output of diff_days?

medium

A. Error

B. 10

C. 11

D. 9

Solution

1. Step 1: Understand TIMESTAMPDIFF with DAY unit

   It counts full days between the two dates, excluding the start date.

2. Step 2: Calculate days between 2024-01-01 and 2024-01-10

   From Jan 1 to Jan 10 is 9 full days difference.

3. Final Answer:

   9 -> Option D

4. Quick Check:

   10 - 1 = 9 days difference [OK]

Hint: TIMESTAMPDIFF counts full units between dates [OK]

Common Mistakes:

• Counting both start and end dates
• Expecting 10 instead of 9
• Confusing with DATEDIFF behavior

4. Identify the error in this query:
SELECT TIMESTAMPDIFF('MINUTE', '2024-04-01 10:00:00', '2024-04-01 11:30:00');

medium

A. TIMESTAMPDIFF cannot use MINUTE as unit

B. Dates must be swapped in order

C. Unit 'MINUTE' should not be in quotes

D. Dates must be in DATE format, not datetime

Solution

1. Step 1: Check TIMESTAMPDIFF unit syntax

   The unit keyword like MINUTE must be unquoted, as a keyword, not a string.

2. Step 2: Validate other parts

   The dates and order are correct; MINUTE is a valid unit; datetime format is allowed.

3. Final Answer:

   Unit 'MINUTE' should not be in quotes -> Option C

4. Quick Check:

   Unit keywords are unquoted [OK]

Hint: Remove quotes around unit in TIMESTAMPDIFF [OK]

Common Mistakes:

• Quoting the unit keyword
• Swapping date order unnecessarily
• Thinking datetime is invalid input

5. You want to find the total number of months between two dates '2023-01-15' and '2024-06-10', but only count full months passed. Which query correctly does this?

hard

A. SELECT DATEDIFF('2024-06-10', '2023-01-15') / 30;

B. SELECT TIMESTAMPDIFF(MONTH, '2023-01-15', '2024-06-10');

C. SELECT TIMESTAMPDIFF(DAY, '2023-01-15', '2024-06-10') / 30;

D. SELECT TIMESTAMPDIFF(YEAR, '2023-01-15', '2024-06-10') * 12;

Solution

1. Step 1: Understand requirement for full months

   We need full months difference, not approximate days divided by 30.

2. Step 2: Check each option

   SELECT TIMESTAMPDIFF(MONTH, '2023-01-15', '2024-06-10'); uses TIMESTAMPDIFF with MONTH unit, which counts full months correctly.
   SELECT DATEDIFF('2024-06-10', '2023-01-15') / 30; and C use days divided by 30, which is approximate and can be wrong.
   SELECT TIMESTAMPDIFF(YEAR, '2023-01-15', '2024-06-10') * 12; counts years times 12, ignoring leftover months.

3. Final Answer:

   SELECT TIMESTAMPDIFF(MONTH, '2023-01-15', '2024-06-10'); -> Option B

4. Quick Check:

   Use TIMESTAMPDIFF with MONTH for full months [OK]

Hint: Use TIMESTAMPDIFF with MONTH for full months difference [OK]

Common Mistakes:

• Dividing days by 30 for months
• Using YEAR unit and multiplying
• Using DATEDIFF which returns days only