Mysql select date having mod result is equal to zero - mysql

Question

My Table is
id name reg_date
1 ABC 2018-08-16
2 PQR 2018-08-10
3 LMN 2018-07-27
4 AAA 2018-01-01
5 BBB 2018-08-11
I want to get all user register on seven days interval before of given date. lets suppose I pass '2017-08-17'. Now I want to pass two date ('2017-08-17','2017-08-19'). so I want which date match betwwen this two date. right now mysql query is
SELECT *
FROM myTable
WHERE
MOD(UNIX_TIMESTAMP(DATE('2017-08-17')) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) = 0
Result will be
id name date match_date
2 PQR 2018-08-10 2017-08-17
3 LMN 2018-07-27 2017-08-17
5 BBB 2018-08-11 2017-08-18

Answer 1

If I understand you correctly, you want to find all dates falling on a 7 day boundary of one or more dates within a range. First appreciate that if your date range is 7 days or greater, then all dates in the table will be returned by definition. Not wanting to give you a solution heavily involving dynamic SQL, I instead chose to use an alternative. For each row I compute whether that date would lie on a boundary with a date in your range. If so, then that record is retained and the matching date from the range is displayed. I encourage you to explore the demo below if you are curious about how this query works.
-- assign the bounds of the date range here
-- note that a range of 7 or more days will by definition simply return all records
SET #start_date = '2017-08-18';
SET #end_date = '2017-08-17';
SELECT
t.id,
t.name,
t.reg_date,
CASE WHEN t.mod1 = 0 THEN #start_date
WHEN t.mod2 = 0 AND #end_date <= #start_date - INTERVAL 1 DAY
THEN #start_date - INTERVAL 1 DAY
WHEN t.mod3 = 0 AND #end_date <= #start_date - INTERVAL 2 DAY
THEN #start_date - INTERVAL 2 DAY
WHEN t.mod4 = 0 AND #end_date <= #start_date - INTERVAL 3 DAY
THEN #start_date - INTERVAL 3 DAY
WHEN t.mod5 = 0 AND #end_date <= #start_date - INTERVAL 4 DAY
THEN #start_date - INTERVAL 4 DAY
WHEN t.mod6 = 0 AND #end_date <= #start_date - INTERVAL 5 DAY
THEN #start_date - INTERVAL 5 DAY
WHEN t.mod7 = 0 AND #end_date <= #start_date - INTERVAL 6 DAY
THEN #start_date - INTERVAL 6 DAY
END AS match_date
FROM
(
SELECT
id,
name,
reg_date,
MOD(UNIX_TIMESTAMP(#start_date) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod1,
MOD(UNIX_TIMESTAMP(#start_date - INTERVAL 1 DAY) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod2,
MOD(UNIX_TIMESTAMP(#start_date - INTERVAL 2 DAY) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod3,
MOD(UNIX_TIMESTAMP(#start_date - INTERVAL 3 DAY) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod4,
MOD(UNIX_TIMESTAMP(#start_date - INTERVAL 4 DAY) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod5,
MOD(UNIX_TIMESTAMP(#start_date - INTERVAL 5 DAY) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod6,
MOD(UNIX_TIMESTAMP(#start_date - INTERVAL 6 DAY) -
UNIX_TIMESTAMP(DATE(reg_date)), 7*24*60*60) AS mod7
FROM yourTable
) t
WHERE
t.mod1 = 0 OR
(t.mod2 = 0 AND #end_date <= #start_date - INTERVAL 1 DAY) OR
(t.mod3 = 0 AND #end_date <= #start_date - INTERVAL 2 DAY) OR
(t.mod4 = 0 AND #end_date <= #start_date - INTERVAL 3 DAY) OR
(t.mod5 = 0 AND #end_date <= #start_date - INTERVAL 4 DAY) OR
(t.mod6 = 0 AND #end_date <= #start_date - INTERVAL 5 DAY) OR
(t.mod7 = 0 AND #end_date <= #start_date - INTERVAL 6 DAY)
Demo here:
Rextester

Answer 2

As i understand your question i think you can use BETWEEN keyword.
where columna_name between date1 AND date2