week range of particular month year using mysql - mysql

Question

I want to show date range of week by passing a variable which contains year and month i.e 2016-07 like this in mysql how could i achieve this:
for eg: if i pass 2016-07 then my output should look like this:
2016-07-03 to 2016-07-10 || 2016-07-11 to 2016-07-17
and so on

Answer 1

There are several parts to solving this problem, when you go to solve it in MySQL.
One is to decide whether your weeks start on Sundays or Mondays. That's a locale-specific business rule. In locales formerly part of the British Empire (USA, India) it's usually Sunday. In other places, it's Monday.
So we'll need a function like this: firstDayOfWeek(date). More about that in a moment.
Once we have that, we'll need a way to get the last day of the month in question. That's easy; it's a built-in MySQL function. LAST_DAY(date)
You have said you'll specify the month in question with a string like 1941-12. We'll need to turn that into a DATE object. That can be done like this:
STR_TO_DATE(CONCAT(`1941-12`, `-01'), '%Y-%m-%d')
We need a virtual table with the integers from 0 to 4. Let's call that table seq_0_to_4. We pick that range of integers because no months have more than five Sundays (or Mondays). More on that later.
OK, these are the conceptual building blocks. Let's use them.
The first day of the week derived from the last day of the month is
SET #month := '1941-12';
SET #first_day_of_month := STR_TO_DATE(CONCAT(`1941-12`, `-01'), '%Y-%m-%d')
SET #seed : =FirstDayOfWeek(LAST_DAY(first_day_of_month));
Then you need four five consecutive week-starting days the last of which is #seed.
SELECT #seed - INTERVAL (7*seq.seq) first_day_of_week
FROM seq_0_to_4
Next you need to limit that to days in your month.
SELECT first_day_of_week,
first_day_of_week + INTERVAL 6 DAY last_day_of_week
FROM (
SELECT #seed - INTERVAL (7*seq.seq) first_day_of_week
FROM seq_0_to_4
) w
WHERE first_day_of_week >= #first_day_of_month
ORDER BY first_day_of_week
That gives you a table of rows, one for each week beginning in the month. If you want to exclude weeks in which the last weekday is in the next month, change your WHERE to
WHERE first_day_of_week >= #first_day_of_month
AND first_day_of_week + INTERVAL 6 DAY <= #seed
Finally, to get the exact string format you specified in your question, wrap that query in this:
SELECT GROUP_CONCAT (
CONCAT(first_day_of_week, ' to ', last_day_of_week)
SEPARATOR ' || '
ORDER BY first_day_of_week)
FROM (
SELECT first_day_of_week,
first_day_of_week + INTERVAL 6 DAY last_day_of_week
FROM (
SELECT #seed - INTERVAL (7*seq.seq) first_day_of_week
FROM seq_0_to_4
) w
WHERE first_day_of_week >= #first_day_of_month
) x
That's it.
I promised to describe FirstDayOfWeek(dt). Here it is.
FROM_DAYS(TO_DAYS(dt) -MOD(TO_DAYS(dt) -1, 7))
It's a bit of a magic spell, but it works. If your weeks start Mondays, it is this.
FROM_DAYS(TO_DAYS(dt) -MOD(TO_DAYS(dt) -2, 7))
I promised to describe seq_0_to_4. If you're using the MariaDB fork of MySQL, it's built in. If you're using the Sun / Oracle fork, you define it like this.
(SELECT 0 AS seq UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4) seq_0_to_4
Putting it all together:
SET #month := '1941-12';
SET #first_day_of_month := STR_TO_DATE(CONCAT(`1941-12`, `-01'), '%Y-%m-%d');
SET #seed := FROM_DAYS(TO_DAYS(LAST_DAY(first_day_of_month))
-MOD(TO_DAYS(LAST_DAY(first_day_of_month)) -1, 7));
SELECT GROUP_CONCAT (
CONCAT(first_day_of_week, ' to ', last_day_of_week)
SEPARATOR ' || '
ORDER BY first_day_of_week)
FROM (
SELECT first_day_of_week,
first_day_of_week + INTERVAL 6 DAY last_day_of_week
FROM (
SELECT #seed - INTERVAL (7*seq.seq) first_day_of_week
FROM (SELECT 0 AS seq UNION SELECT 1 UNION SELECT 2
UNION SELECT 3 UNION SELECT 4
) seq
) w
WHERE first_day_of_week >= #first_day_of_month
) x
It's unreasonably complex (the technical term is a freakin' hairball) to solve your problem in pure MySQL-dialect SQL, but it's possible.

Answer 2

Probably is too late but i figured out this using Common Table expressions in MYSQL 8.0.2
WITH RECURSIVE
Years(y) AS
(
SELECT 2020
UNION ALL
SELECT y + 1 FROM Years WHERE y < 2021
),
Days (d) AS
(
SELECT 1
UNION ALL
SELECT d + 1 FROM Days WHERE d < 366
)
SELECT
y AS Year,
MONTH(MakeDate(y,d)) AS Month,
WEEK(MakeDate(y,d))+1 -WEEK(TIMESTAMPADD(MONTH,MONTH(MakeDate(y,d))-1,MakeDate(y,1))) AS Week,
Min(MakeDate(y,d)) AS StartDate,
timestampadd(second,-1,timestampadd(day,1,MAx(MakeDate(y,d)))) AS EndDate
FROM Years,Days
WHERE Year(MakeDate(y,d)) <= y
GROUP BY y, MONTH(MakeDate(y,d)),WEEK(MakeDate(y,d))+1 -WEEK(TIMESTAMPADD(MONTH,MONTH(MakeDate(y,d))-1,MakeDate(y,1)))
ORDER BY 1,2,3