Find missing rows between three related tables - sql

Question

I have three tables:
Person
person_id
-------------
10001
10002
10003
10004
Dates
date_type date
-------------- -----------------------
PUBLIC_HOLIDAY 2020-04-10 00:00:00.000
PUBLIC_HOLIDAY 2020-04-13 00:00:00.000
Absence
person_id date absence_type
--------- ----------------------- ------------
10001 2020-04-10 00:00:00.000 HOLIDAY
10001 2020-04-13 00:00:00.000 HOLIDAY
10002 2020-04-10 00:00:00.000 HOLIDAY
10003 2020-04-13 00:00:00.000 HOLIDAY
I need to find all of the person_id's in the Person table and the date's from the Dates table who have not booked any absence matching the following criteria:
Dates.date_type = 'PUBLIC_HOLIDAY'
Absence.absence_type = 'HOLIDAY'
Basically, I need to find the people and the dates which are public holidays they have not booked an absence for as holiday.

Answer 1

You can try this below logic-
DEMO HERE
SELECT Person.person_id,Dates.dat,ISNULL(Absence.dat, 'Not Bokked')
FROM Dates
CROSS JOIN Person
LEFT JOIN Absence ON Person.person_id = Absence.person_id AND Dates.dat = Absence.dat
WHERE Dates.date_type = 'PUBLIC_HOLIDAY'
If you wants only information with not booked, just simply add below line to the script-
AND Absence.dat IS NULL

Answer 2

I think that you want a cross join to generate all combinations of persons and dates, and then not exists to filter on those that do not exist in the absence table:
select p.*, d.*
from person p
cross join dates d
where
d.date_type = 'PUBLIC_HOLIDAY'
and not exists (
select 1
from absence a
where a.person_id = p.person_id and a.date = d.date and a.absence_type = 'HOLIDAY'
)

Answer 3

Try:
select distinct person_id from absence a
where absence_type = 'HOLIDAY'
and not exists (select 1 from dates
where date = a.date
and date_type = 'PUBLIC_HOLIDAY')
union all
select person_id from person p
where not exists ( select 1 from absence
where p.person_id = person_id)
If you want to have them with dates, use below query:
select person_id, date from absence a
where absence_type = 'HOLIDAY'
and not exists (select 1 from dates
where date = a.date
and date_type = 'PUBLIC_HOLIDAY')
union all
-- in person table we don;t have any dates
select person_id, null from person p
where not exists ( select 1 from absence
where p.person_id = person_id)

Answer 4

you can use below query. I have tested this in SQL Server 2014.
CREATE TABLE #Person(person_id INT)
INSERT INTO #person
values
(10001),
(10002),
(10003),
(10004);
CREATE TABLE #Dates (date_Type VARCHAR(50), [datevalue] datetime)
INSERT INTO #Dates
VALUES
('PUBLIC_HOLIDAY','2020-04-10 00:00:00.000'),
('PUBLIC_HOLIDAY','2020-04-13 00:00:00.000');
CREATE TABLE #Absence (person_id int, datevalue datetime, absence_type VARCHAR(50))
INSERT INTO #Absence
VALUES
(10001,'2020-04-10 00:00:00.000','HOLIDAY'),
(10001,'2020-04-13 00:00:00.000','HOLIDAY'),
(10002,'2020-04-10 00:00:00.000','HOLIDAY'),
(10003,'2020-04-13 00:00:00.000','HOLIDAY');
SELECT p.person_id, od.datevalue
FROM #Person AS p
CROSS JOIN (SELECT * FROM #Dates WHERE date_type ='PUBLIC_HOLIDAY') AS od
WHERE NOT EXISTS
(
SELECT 1 FROM
#Absence AS a
INNER JOIN #Dates AS d
ON a.datevalue = d.datevalue
WHERE a.absence_type = 'Holiday' AND d.date_type = 'PUBLIC_HOLIDAY'
AND a.person_id = p.person_id and d.datevalue = od.datevalue)
Below is the resultset:
+-----------+-------------------------+
| person_id | datevalue |
+-----------+-------------------------+
| 10003 | 2020-04-10 00:00:00.000 |
| 10004 | 2020-04-10 00:00:00.000 |
| 10002 | 2020-04-13 00:00:00.000 |
| 10004 | 2020-04-13 00:00:00.000 |
+-----------+-------------------------+