DATE_FORMAT function in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the DATE_FORMAT function do in MySQL?

It formats a date or datetime value according to a specified format string, returning the result as text.

beginner

How do you format a date to show only the year using DATE_FORMAT?

Use DATE_FORMAT(date, '%Y') to get the 4-digit year from a date.

intermediate

What format specifier would you use in DATE_FORMAT to display the month as a full name?

Use %M to display the full month name, like 'January' or 'February'.

intermediate

Write a DATE_FORMAT example to display a date as 'Day-Month-Year', like '05-April-2024'.

Use DATE_FORMAT(date, '%d-%M-%Y') to format the date as '05-April-2024'.

intermediate

Can DATE_FORMAT be used to format time parts like hours and minutes?

Yes, you can use specifiers like %H for hours and %i for minutes to format time.

Which format specifier in DATE_FORMAT returns the full month name?

A %M

B %m

C %b

D %d

The specifier %M returns the full month name, like 'January'. %m returns the month number, %b returns abbreviated month name, and %d returns the day of the month.

What will DATE_FORMAT('2024-06-15', '%Y-%m-%d') return?

A 15-06-2024

B 06/15/2024

C June 15, 2024

D 2024-06-15

The format '%Y-%m-%d' returns the date in 'year-month-day' numeric format, so it returns '2024-06-15'.

Which DATE_FORMAT specifier shows the hour in 24-hour format?

A %h

B %I

C %H

D %p

%H returns the hour in 24-hour format (00 to 23). %h and %I are 12-hour formats, and %p is AM/PM.

How would you format a date to show 'Friday, 05 April 2024' using DATE_FORMAT?

A %w, %d %m %Y

B %W, %d %M %Y

C %D, %d %M %Y

D %A, %d %M %Y

%W returns the weekday name, %d the day, %M the full month name, and %Y the year. %A is not a valid specifier in MySQL.

What type of value does DATE_FORMAT return?

A String

B Datetime

C Integer

D Date

DATE_FORMAT returns a string formatted according to the format specifiers.

Explain how the DATE_FORMAT function works and give an example of formatting a date to 'YYYY/MM/DD'.

Think about how you tell MySQL to show a date in a specific way.

List at least three different format specifiers used in DATE_FORMAT and what they represent.

Remember specifiers are like codes that tell MySQL what part of the date/time to show.

Practice

1. What does the MySQL function DATE_FORMAT(date, format) do?

easy

A. It calculates the difference between two dates.

B. It converts a string to a date type.

C. It adds days to a date value.

D. It changes how a date or time is displayed using a specific pattern.

Solution

1. Step 1: Understand the function purpose

   The DATE_FORMAT function is used to display dates in a specific format by applying a pattern string.

2. Step 2: Compare options with function behavior

   Only It changes how a date or time is displayed using a specific pattern. correctly describes changing the display format of a date/time value.

3. Final Answer:

   It changes how a date or time is displayed using a specific pattern. -> Option D

4. Quick Check:

   DATE_FORMAT changes display format = A [OK]

Hint: DATE_FORMAT changes date display style, not date value [OK]

Common Mistakes:

• Confusing DATE_FORMAT with date arithmetic functions
• Thinking it converts strings to dates
• Assuming it calculates date differences

2. Which of the following is the correct syntax to format a date as 'Year-Month-Day' using DATE_FORMAT?

easy

A. DATE_FORMAT(date, '%Y-%m-%d')

B. DATE_FORMAT(date, 'YYYY-MM-DD')

C. DATE_FORMAT(date, '%y/%M/%d')

D. DATE_FORMAT(date, 'YY-MM-DD')

Solution

1. Step 1: Recall correct format specifiers

   In MySQL, '%Y' is 4-digit year, '%m' is 2-digit month, '%d' is 2-digit day.

2. Step 2: Check each option's format string

   Only DATE_FORMAT(date, '%Y-%m-%d') uses correct MySQL format specifiers and separators for 'Year-Month-Day'. Others use invalid or wrong specifiers.

3. Final Answer:

   DATE_FORMAT(date, '%Y-%m-%d') -> Option A

4. Quick Check:

   Use %Y-%m-%d for year-month-day [OK]

Hint: Use %Y for year, %m for month, %d for day in DATE_FORMAT [OK]

Common Mistakes:

• Using uppercase YYYY instead of %Y
• Mixing format codes from other languages
• Using wrong separators like slashes instead of dashes

3. Given the query:
SELECT DATE_FORMAT('2024-06-15 14:30:00', '%W, %M %d, %Y %r') AS formatted_date;
What is the expected output in the formatted_date column?

medium

A. Sun, Jun 15, 2024 02:30 PM

B. Saturday, June 15, 2024 02:30:00 PM

C. Saturday, June 15, 2024 14:30:00

D. 2024-06-15 14:30:00

Solution

1. Step 1: Understand each format specifier

   %W = full weekday name (Saturday), %M = full month name (June), %d = day (15), %Y = year (2024), %r = 12-hour time with seconds and AM/PM (02:30:00 PM).

2. Step 2: Apply format to given datetime

   The datetime '2024-06-15 14:30:00' is 2:30 PM in 12-hour format, so output matches Saturday, June 15, 2024 02:30:00 PM exactly.

3. Final Answer:

   Saturday, June 15, 2024 02:30:00 PM -> Option B

4. Quick Check:

   Full weekday, month, and 12-hour time = C [OK]

Hint: Remember %r gives 12-hour time with seconds and AM/PM [OK]

Common Mistakes:

• Confusing %r with 24-hour time %H:%i:%s
• Using abbreviated weekday (%a) instead of full (%W)
• Ignoring AM/PM in output

4. Identify the error in this query:
SELECT DATE_FORMAT('2024-06-15', '%Y-%m-%d %H:%i:%s') AS formatted_date;
What will happen when this query runs?

medium

A. It will return NULL because the input has no time part.

B. It will cause a syntax error due to wrong format specifiers.

C. It will return '2024-06-15 00:00:00' as the time defaults to midnight.

D. It will return only the date part ignoring the time format.

Solution

1. Step 1: Analyze input and format

   The input date '2024-06-15' has no time, but MySQL treats missing time as '00:00:00'. Format includes time specifiers %H:%i:%s.

2. Step 2: Predict output behavior

   MySQL fills missing time with zeros, so output will be '2024-06-15 00:00:00'. No syntax error occurs.

3. Final Answer:

   It will return '2024-06-15 00:00:00' as the time defaults to midnight. -> Option C

4. Quick Check:

   Missing time defaults to 00:00:00 in DATE_FORMAT [OK]

Hint: Missing time defaults to 00:00:00, no error [OK]

Common Mistakes:

• Expecting syntax error for valid format
• Assuming NULL output for missing time
• Ignoring default midnight time fill

5. You want to display a datetime column created_at as 'Day-Month-Year Hour:Minute AM/PM' in a report. Which DATE_FORMAT pattern correctly formats it as '15-Jun-2024 02:30 PM'?

hard

A. DATE_FORMAT(created_at, '%d-%b-%Y %h:%i %p')

B. DATE_FORMAT(created_at, '%d-%m-%Y %H:%i %p')

C. DATE_FORMAT(created_at, '%d-%M-%Y %h:%i %P')

D. DATE_FORMAT(created_at, '%d-%b-%Y %H:%i %p')

Solution

1. Step 1: Match each format code to desired output

   %d = day with leading zero (15), %b = abbreviated month name (Jun), %Y = 4-digit year (2024), %h = 12-hour hour (02), %i = minutes (30), %p = AM/PM uppercase.

2. Step 2: Check options for correct codes and case

   DATE_FORMAT(created_at, '%d-%b-%Y %h:%i %p') matches all codes correctly. DATE_FORMAT(created_at, '%d-%m-%Y %H:%i %p') uses %m (numeric month) instead of %b. DATE_FORMAT(created_at, '%d-%M-%Y %h:%i %P') uses %M (full month) and %P (invalid). DATE_FORMAT(created_at, '%d-%b-%Y %H:%i %p') uses %H (24-hour) instead of %h.

3. Final Answer:

   DATE_FORMAT(created_at, '%d-%b-%Y %h:%i %p') -> Option A

4. Quick Check:

   Use %b for short month, %h for 12-hour, %p for AM/PM [OK]

Hint: Use %b for short month, %h for 12-hour, %p for AM/PM [OK]

Common Mistakes:

• Using %m instead of %b for month name
• Using %H (24-hour) instead of %h (12-hour)
• Using %P which is invalid in MySQL