What is the MySQL alternative to Oracle's NEXT_DAY function? - mysql

Question

NEXT_DAY("01-SEP-95","FRIDAY") returns what is the date on next Friday, but in MySQL this function does not seem to be appear. What is the alternative?

Answer 1

I'm going to throw my hat in the ring with yet another approach:
Edit: I realize somewhat belatedly that the Oracle function in question takes a string as the second argument, and so this doesn't precisely fit the requirement. However MySQL has already kindly defined 0 - 6 as Monday - Sunday, and anyway I have moral objections to using a string as an argument for this type of thing. A string would either come from user input or yet another mapping in higher level code between numeric and string values. Why not pass an integer? :)
CREATE FUNCTION `fnDayOfWeekGetNext`(
p_date DATE,
p_weekday TINYINT(3)
) RETURNS date
BEGIN
RETURN DATE_ADD(p_date, INTERVAL p_weekday - WEEKDAY(p_date) + (ROUND(WEEKDAY(p_date) / (p_weekday + WEEKDAY(p_date) + 1)) * 7) DAY);
END
To break the portion down that determines the INTERVAL value:
The first part of the equation simply gets the offset between the weekday specified and the weekday of the date specified:
p_weekday - WEEKDAY(p_date)
This will return a positive number if p_weekday is greater than WEEKDAY(p_date) and vice versa. Zero will be returned if they're the same.
The ROUND() segment is used to determine whether the requested day of the week (p_weekday) has already occurred in the current week relative to the date (p_date) specified. So, by example...
ROUND(WEEKDAY('2019-01-25') / (6 + WEEKDAY('2019-01-25') + 1))
..returns 0, indicating that Sunday (6) has not occurred this week, as 2019-01-25 is a Friday. Likewise...
ROUND(WEEKDAY('2019-01-25') / (2 + WEEKDAY('2019-01-25') + 1))
...returns 1 because Wednesday (2) has already passed. Note that this will return 0 if p_weekday is the same as the weekday of p_date.
This value (either 1 or 0) is then multiplied by the constant 7 (the number of days in a week).
Hence if p_weekday has already occurred in the current week, it will add 7 to the offset p_weekday - WEEKDAY(p_date), because that offset would be a negative number and we want a date in the future.
If p_weekday has yet to occur in the current week, then we can just add the offset to the current date because the offset will be a positive number. Hence the section ROUND(...) * 7 is equal to zero and, in essence, ignored.
My desire for this approach was to simulate an IF() condition mathematically. This would be equally valid:
RETURN DATE_ADD(p_date, INTERVAL p_weekday - WEEKDAY(p_date) + IF(p_weekday - WEEKDAY(p_date) < 0, 7, 0) DAY);
And in the interest of objectivity, in running 1M iterations a few times of each function the IF-based version averaged about 4.2% faster than the ROUND-based version.

Answer 2

In MySQL, you can create user defined function
DELIMITER //
 
CREATE FUNCTION next_day(start_date DATETIME, weekday CHAR(20))
RETURNS DATETIME
BEGIN
DECLARE start DATETIME;
DECLARE i INT;
 
// Select the next date
SET start = ADDDATE(start_date, 1);
SET i = 1;
 
days: LOOP
-- Compare the day names
IF SUBSTR(DAYNAME(start), 1, 3) = SUBSTR(weekday, 1, 3) THEN
LEAVE days;
END IF;
 
// Select the next date
SET start = ADDDATE(start, 1);
SET i = i + 1;
 
-- Not valid weekday specified
IF i > 7 THEN
SET start = NULL;
LEAVE days;
END IF;
 
END LOOP days;
 
RETURN start;
END;
//
 
DELIMITER ;
and call it
SELECT NEXT_DAY("1995-09-01","FRIDAY")
Source : http://www.sqlines.com/mysql/how-to/next_day

Answer 3

Here's an answer to a different problem:
Find the date for Friday of the current week:-
SELECT STR_TO_DATE(CONCAT('2017',(SELECT DATE_FORMAT(CURDATE(),'%U')),' Friday'),'%Y %U %W') x;
+------------+
| x |
+------------+
| 2017-05-12 |
+------------+
The above hasn't been verified for robustness, but is provided 'as is' merely as food for thought.

Answer 4

SQL Fiddle
MySQL 5.6 Schema Setup:
CREATE TABLE your_table ( value DATE );
INSERT INTO your_table ( value )
SELECT DATE '2017-05-08' FROM DUAL UNION ALL
SELECT DATE '2017-05-09' FROM DUAL UNION ALL
SELECT DATE '2017-05-10' FROM DUAL UNION ALL
SELECT DATE '2017-05-11' FROM DUAL UNION ALL
SELECT DATE '2017-05-12' FROM DUAL UNION ALL
SELECT DATE '2017-05-13' FROM DUAL UNION ALL
SELECT DATE '2017-05-14' FROM DUAL;
Query 1:
SELECT value,
ADDDATE(
value,
6 - DAYOFWEEK( value )
+ CASE WHEN DAYOFWEEK( value ) < 6 THEN 0 ELSE 7 END
) AS next_friday
FROM your_table
Results:
| value | next_friday |
|-----------------------|-----------------------|
| May, 08 2017 00:00:00 | May, 12 2017 00:00:00 |
| May, 09 2017 00:00:00 | May, 12 2017 00:00:00 |
| May, 10 2017 00:00:00 | May, 12 2017 00:00:00 |
| May, 11 2017 00:00:00 | May, 12 2017 00:00:00 |
| May, 12 2017 00:00:00 | May, 19 2017 00:00:00 |
| May, 13 2017 00:00:00 | May, 19 2017 00:00:00 |
| May, 14 2017 00:00:00 | May, 19 2017 00:00:00 |

Answer 5

Short Version:
Utilizing DAYOFWEEK() you can leverage the number values to create a closed formula that tells you how many days to add. You can then utilize DATE_ADD to help you shift the date. There may be a cleaner way, however you should be able to make a function out of this.
The following is an Excel formula, which you use to verify all 49 use cases: =MOD(MOD(Next-Input, 7)+7,7)
Some examples of how the excel calculations can be translated into SQL:
SELECT (((1-DAYOFWEEK('2018-08-15')) % 7)+7) % 7 AS DaysToAddToGetNextSundayFromWednesday
FROM dual; -- 4
SELECT DATE_ADD('2018-08-15', INTERVAL (((1-DAYOFWEEK('2018-08-15')) % 7)+7) % 7 DAY) AS NextSundayFromDate
FROM dual; -- 2018-08-19
If you plan to use the above often, you'll probably want to make a function or stored procedure.
Long Version:
I've run into this problem multiple times over the years. First time I created a giant case statement for all 49 cases. I found that this made the queries super big and not clean. I wanted a cleaner, simpler solution like a closed in formula. Below are details to to calculations I did to confirm the formula above works. I tested this with MySQL 5.7 if you are using MySQL 8.5 it looks like the function is built in ( Reference: http://www.sqlines.com/mysql/how-to/next_day ).
Note: Excel doesn't return negative results for modulus, where MySQL does. That is why we add 7 and do another modulus.
DAYOFWEEK()
Sun 1
Mon 2
Tues 3
Wed 4
Thur 5
Fri 6
Sat 7
Input Next Expected Days to Add Formula Result
1 1 0 0
1 2 1 1
1 3 2 2
1 4 3 3
1 5 4 4
1 6 5 5
1 7 6 6
2 1 6 6
2 2 0 0
2 3 1 1
2 4 2 2
2 5 3 3
2 6 4 4
2 7 5 5
3 1 5 5
3 2 6 6
3 3 0 0
3 4 1 1
3 5 2 2
3 6 3 3
3 7 4 4
4 1 4 4
4 2 5 5
4 3 6 6
4 4 0 0
4 5 1 1
4 6 2 2
4 7 3 3
5 1 3 3
5 2 4 4
5 3 5 5
5 4 6 6
5 5 0 0
5 6 1 1
5 7 2 2
6 1 2 2
6 2 3 3
6 3 4 4
6 4 5 5
6 5 6 6
6 6 0 0
6 7 1 1
7 1 1 1
7 2 2 2
7 3 3 3
7 4 4 4
7 5 5 5
7 6 6 6
7 7 0 0