DATE_FORMAT and EXTRACT in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SQL function DATE_FORMAT do?

DATE_FORMAT formats a date or datetime value into a string based on a specified pattern. It helps you display dates in a readable or custom way.

beginner

What is the purpose of the SQL function EXTRACT?

EXTRACT pulls out a specific part (like year, month, day) from a date or time value. It returns that part as a number.

beginner

Write a simple example of DATE_FORMAT to show a date as 'Day-Month-Year'.

Example: DATE_FORMAT('2024-06-15', '%d-%m-%Y') returns '15-06-2024'.

beginner

How do you extract the month from a date using EXTRACT?

Use EXTRACT(MONTH FROM date_column). It returns the month number (1 to 12).

intermediate

What is the difference between DATE_FORMAT and EXTRACT?

DATE_FORMAT converts a date to a formatted string. EXTRACT gets a numeric part from a date (like year or day).

Which SQL function would you use to get the year from a date?

A FORMAT_DATE(date, 'year')

B DATE_FORMAT(date, '%Y-%m-%d')

C GETYEAR(date)

D EXTRACT(YEAR FROM date)

EXTRACT(YEAR FROM date) returns the year as a number. The others are incorrect or invalid.

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

A '15/06/2024'

B '2024/06/15'

C '06/15/2024'

D '15-06-2024'

The format %d/%m/%Y means day/month/year, so it returns '15/06/2024'.

Which part can EXTRACT NOT get from a date?

A MONTH

B WEEKDAY_NAME

C HOUR

D YEAR

EXTRACT can get numeric parts like YEAR, MONTH, HOUR but not text like weekday name.

If you want to display a date as 'June 15, 2024', which function helps best?

A EXTRACT

B NOW()

C DATE_FORMAT

D DATEDIFF

DATE_FORMAT formats dates into readable strings like 'June 15, 2024'.

What type of value does EXTRACT return?

A Number

B Date

C String

D Boolean

EXTRACT returns a number representing the part of the date (like month number).

Explain how to use DATE_FORMAT to change the display of a date.

Think about turning a date into a string with a pattern.

Describe how EXTRACT helps when working with dates in SQL.

Focus on getting specific parts from a date.

Practice

1. What does the SQL function EXTRACT(MONTH FROM '2024-06-15') return?

easy

A. '2024-06-15'

B. 15

C. 2024

D. 6

Solution

1. Step 1: Understand EXTRACT function

   The EXTRACT function pulls out a specific part of a date, here the MONTH part.

2. Step 2: Apply EXTRACT to the date

   From the date '2024-06-15', the month is 6 (June).

3. Final Answer:

   6 -> Option D

4. Quick Check:

   EXTRACT(MONTH FROM date) = 6 [OK]

Hint: EXTRACT pulls one date part, like month or year [OK]

Common Mistakes:

• Confusing day with month
• Expecting full date instead of part
• Using wrong syntax for EXTRACT

2. Which of the following is the correct syntax to get the year from a date using EXTRACT in SQL?

easy

A. EXTRACT(YEAR FROM '2024-06-15')

B. EXTRACT YEAR FROM '2024-06-15'

C. EXTRACT('YEAR', '2024-06-15')

D. EXTRACT('2024-06-15' FROM YEAR)

Solution

1. Step 1: Recall EXTRACT syntax

   The correct syntax is EXTRACT(part FROM date), with parentheses and FROM keyword.

2. Step 2: Check each option

   EXTRACT(YEAR FROM '2024-06-15') matches the correct syntax: EXTRACT(YEAR FROM '2024-06-15'). Others miss parentheses or have wrong order.

3. Final Answer:

   EXTRACT(YEAR FROM '2024-06-15') -> Option A

4. Quick Check:

   Correct EXTRACT syntax uses parentheses and FROM [OK]

Hint: EXTRACT needs parentheses and FROM keyword [OK]

Common Mistakes:

• Omitting parentheses
• Swapping arguments order
• Using quotes around part name

3. What is the output of this SQL query?

SELECT DATE_FORMAT('2024-06-15', '%Y-%m-%d'), EXTRACT(DAY FROM '2024-06-15');

medium

A. 2024-06-15, 6

B. 2024-06-15, 15

C. 2024/06/15, 15

D. 06-15-2024, 15

Solution

1. Step 1: Understand DATE_FORMAT with '%Y-%m-%d'

   This format outputs year-month-day as '2024-06-15'.

2. Step 2: Understand EXTRACT(DAY FROM date)

   Extracting DAY from '2024-06-15' gives 15.

3. Final Answer:

   2024-06-15, 15 -> Option B

4. Quick Check:

   DATE_FORMAT + EXTRACT day = '2024-06-15', 15 [OK]

Hint: DATE_FORMAT '%Y-%m-%d' matches original date format [OK]

Common Mistakes:

• Mixing month and day order
• Wrong format string in DATE_FORMAT
• Extracting wrong date part

4. Identify the error in this SQL query:

SELECT DATE_FORMAT('2024-06-15', '%Y-%d-%m');

medium

A. The date string must be in MM-DD-YYYY format

B. DATE_FORMAT requires three arguments

C. The format string swaps day and month incorrectly

D. EXTRACT should be used instead of DATE_FORMAT

Solution

1. Step 1: Analyze the format string '%Y-%d-%m'

   This format prints year, then day, then month, which is unusual and likely a mistake.

2. Step 2: Understand common date format order

   Usually, month comes before day as '%Y-%m-%d'. Swapping day and month causes confusing output.

3. Final Answer:

   The format string swaps day and month incorrectly -> Option C

4. Quick Check:

   Correct order is year-month-day, not year-day-month [OK]

Hint: Check format order: month before day usually [OK]

Common Mistakes:

• Mixing day and month in format string
• Wrong number of arguments to DATE_FORMAT
• Confusing DATE_FORMAT with EXTRACT

5. You want to list all orders from a table orders showing only the year and month of the order date in format YYYY-MM. Which SQL query correctly does this?

hard

A. SELECT DATE_FORMAT(order_date, '%Y-%m') AS year_month FROM orders;

B. SELECT EXTRACT(YEAR_MONTH FROM order_date) AS year_month FROM orders;

C. SELECT DATE_FORMAT(order_date, '%Y-%d') AS year_month FROM orders;

D. SELECT EXTRACT(MONTH FROM order_date) AS year_month FROM orders;

Solution

1. Step 1: Understand DATE_FORMAT for year and month

   Using '%Y-%m' in DATE_FORMAT returns year and month as 'YYYY-MM'.

2. Step 2: Check other options

   SELECT EXTRACT(YEAR_MONTH FROM order_date) AS year_month FROM orders; is invalid syntax; EXTRACT does not support YEAR_MONTH. SELECT DATE_FORMAT(order_date, '%Y-%d') AS year_month FROM orders; uses day instead of month. SELECT EXTRACT(MONTH FROM order_date) AS year_month FROM orders; returns only month number, missing year.

3. Final Answer:

   SELECT DATE_FORMAT(order_date, '%Y-%m') AS year_month FROM orders; -> Option A

4. Quick Check:

   DATE_FORMAT with '%Y-%m' gives year-month [OK]

Hint: Use DATE_FORMAT with '%Y-%m' for year and month [OK]

Common Mistakes:

• Using EXTRACT with unsupported parts
• Mixing day and month in format
• Selecting only month without year