Ok, here's the thing. I have the Following tables involved :
> YEARS
------------------------------
ID YEAR ACTUAL
------------------------------
1 2014-15 TRUE
2 2015-16 FALSE
> SHOPS
------------------------------
ID NAME ...
------------------------------
1 ThisShop ...
> ITA
------------------------------
ID YEAR_ID SHOP_ID
------------------------------
1 1 1
2 1 2
...
> INSPECTORS
------------------------------
ID INSPECTOR
------------------------------
1 M. Black
2 M. White
3 M. Brown
...
> ITA_INSPECTORS
-------------------------------------------------------
ID ID_ITA ID_INSPCTR StartDate EndDate
-------------------------------------------------------
Here's the thing, I want a query to display ALL the INSPECTORS, listed or not in ITA_INSPECTORS for the SHOPS ID = 1 AND YEARS ID = 1. If the inspector is present in the ITA_INSPECTORS table, show the Start and End dates, if not, show without the dates.
Note that there might not be an ITA_ID in the ITA_INSPECTORS table for a selected shop (imagine the ITA_INSPECTORS table is empty, I wouls still need to view all of the INSPECTOR names).
The INSPECTORS table is static data to build the ITA_INSPECTORS table.
I have tried this query :
SELECT * FROM ((ITA
INNER JOIN YEARS ON ITA.ID_YEAR = YEARS.ID)
LEFT JOIN ITA_INSPECTORS ON ITA.ID = ITA_INSPECTORS.ID_ITA)
RIGHT JOIN INSPECTORS ON ITA_INSPECTORS.ID_INSPCTR = INSPECTORS.ID
WHERE ITA.SHOP_ID = 1 AND ((YEARS.ACTUAL) = True);
It works until I add the RIGHT JOIN clause, then I get an error saying Join expression not supported.
Can anybody guide me to the proper way of doing this?
Well one solution is to split the query so that it doesn't have these conflicting joins
So create a query e.g q1
SELECT *
FROM (
(
ITA INNER JOIN YEARS ON ITA.ID_YEAR = YEARS.ID
) LEFT JOIN ITA_INSPECTORS ON ITA.ID = ITA_INSPECTORS.ID_ITA
)
and then create a 2nd query to make the right join you need
SELECT INSPECTORS.ID, INSPECTORS.INSPECTOR, q1.*
FROM INSPECTORS LEFT JOIN q1 ON INSPECTORS.ID = q1.ID_ITA;
Related
I used full join and left join to join the Person, Tasks and Task tables. The result shown on the screen resulted in a number of lines greater than six. Unset fields have the value NULL and that's good.
The expected output can be obtained using such joins, however it is necessary to use clauses that allow the common fields to be joined. How can I do this?
A CROSS JOIN produces all the combinations you want. Then a simple outer join can retrieve the related rows (should they exist).
You don't mention the database you are using so a faily standard query will do. For example (in PostgreSQL):
select
row_number() over(order by p.id, t.id) as id,
p.name,
case when x.st is not null then t.hr end,
x.st
from person p
cross join tasks t
left join task x on x.personid_fk = p.id and x.taskid_fk = t.id
order by p.id, t.id;
Result:
id name case st
--- ----- ------ -----
1 Anna null null
2 Anna null null
3 Luo 13:00 true
4 Luo 14:00 false
5 John null null
6 John null null
See running example at DB Fiddle.
A Pupil table with { ID, LastName}
a Subject Table with {ID, SubjectName}
and a Report Table with {ID, PupilID, SubjectID, Grade}
There is a one-to-many relationship between Pupil and Report Tables, and Subject and Report Tables.
I want to generate a table like this for say subjectID = 1
Pupil.ID Pupil.LastName SubjectID Grade
1 --------------Smith ---------- 1 ------------B
2 --------------Jones ---------- 1 ------------NULL
3 -------------Weston ----------1 ------------NULL
4 -------------Knightly ---------1 -----------A
The problem is that the Report table would contain just 2 entries for subject 1:
PupilID SubjectID Grade
----1------- 1 ----------- B
----4------- 1 ----------- A
Left joins don't seem to work since there are only 2 entries in the report table for subject 1
SAMPLE DATA
{Pupil Table}
ID LastName
1 ...Smith
2 ...Jones
3 ...Weston
4 ...Knightly
{Subject Table}
ID SubjectName
1 ....Maths
2 ....Physics
3 ....Chemistry
{Report Table}
ID PupilID SubjectID Grade
1 .......1 ..........1 ..........B
2 .......4 ..........1 ..........A
When I do a search on SubjectID = 1 I want the table:
Pupil.ID .......Pupil.LastName ........SubjectID ...........Grade
1 --------------Smith ---------- 1 ------------B
2 --------------Jones ---------- 1 ------------NULL
3 -------------Weston ----------1 ------------NULL
4 -------------Knightly ---------1 -----------A
Access doesn't do subqueries very easily, so everything gets crammed into the FROM clause with a series of wrapped parentheses. Based on your sample data and my fighting Access to stop being unnecessarily difficult, I came up with this:
SELECT ps.Pupil_ID, ps.LastName, ps.Subject_ID, r.Grade
FROM (SELECT * FROM (SELECT ID AS Pupil_ID, LastName FROM Pupil) p,
(SELECT DISTINCT ID AS Subject_ID FROM Subject)) ps
LEFT JOIN REPORT r ON r.PupilID = ps.Pupil_ID AND r.SubjectID = ps.Subject_ID
ORDER BY Pupil_ID, Subject_ID;
The subquery "ps" is a cartesian join of the Pupil and Subject table views that I specified. At this point, your query would look like this:
(LastName column not shown for clarity)
StudentID|SubjectID
1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3
Now, using that Cartesian join subquery (pupilstudent -> ps), I use a LEFT JOIN to assign the Report table to each unique student's ID and subject ID. Therefore, if a student did not take a particular class, there will be a NULL value in the final result.
I tested this in Access using your sample data and it works on my machine.
Also as a note, it is poor practice to have a field called just ID in each table (e.g. in the Pupil table, ID becomes PupilID). This makes it much easier to use, and it self documents.
Cross join pupil and subject tables and left join result to report table
What you need is a cross join:
SELECT Pupil.ID, Pupil.LastName, SubjectID, Grade FROM
Pupil, Subject LEFT JOIN Report ON Subject.ID=Report.SubjectID
WHERE Subject.ID=1
To combine every pupil with every (or with a particular) subject, use cross join; Then use left join to get the corresponding grades:
select *
from pupil p cross join (select * from subject where id = 1) s
left join report on subjectId = s.id and pupilId = p.id
If I have the following sample table (order by ID)
ID Date Type
-- ---- ----
1 01/01/2000 A
2 22/04/1995 A
2 14/02/2001 B
Where you can immediate see that ID=1 does not have a Type=B, but ID=2 does. What I want to do, if fill in a line to show this:
ID Date Type
-- ---- ----
1 01/01/2000 A
1 NULL B
2 22/04/1995 A
2 14/02/2001 B
where there could potentially be 100's of different types, (so may need to end up inserting 100's rows per person if they lack 100's Types!)
Is there a general solution to do this?
Could I possibly outer join the table on itself and do it that way?
You can do this with a cross join to generate all the rows and a left join to get the actual data values:
select i.id, s.date, t.type
from (select distinct id from sample) i cross join
(select distinct type from sample) t left join
sample s
on s.id = i.id and
s.type = t.type;
I have a simple SQL query I just get to work out right. I've put together a test database like this;
TABLE MAIN
id name groupone grouptwo
1 Fred 1 3
2 bob 2 1
TABLE DETAIL
id group groupname
1 1 onegrp
2 2 twogrp
4 3 threegrp
My Select query is;
SELECT name, groupone, grouptwo, groupname
FROM main
INNER JOIN detail
ON main.groupone = detail.group
WHERE main.id = 1
The result I get is;
id name groupone grouptwo groupname
1 fred 1 3 onegrp
How do I change this to instead of giving the result as 1 and 3.
I get ... fred onegrp, threegrp
I've tried a dozen things but can't get it to work, I sort of want a give me the groupname again option but not sure what the syntax is for that! :(
Thanks in advance for your time and help
I think this is what you are after. You need to join the detail table twice, on the two different keys.
SELECT
m.Name
,a.groupname as 'GroupOne'
,b.groupname as 'GroupTwo'
FROM
main m
INNER JOIN
detail a
on m.groupone = a.group
INNER JOIN
detail b
on m.grouptwo = b.group
WHERE
m.id = 1
My question is quite similar to Restricting a LEFT JOIN, with a variation.
Assuming I have a table SHOP and another table LOCATION. Location is a sort of child table of table SHOP, that has two columns of interest, one is a Division Key (calling it just KEY) and a "SHOP" number. This matches to the Number "NO" in table SHOP.
I tried this left outer join:
SELECT S.NO, L.KEY
FROM SHOP S
LEFT OUTER JOIN LOCATN L ON S.NO = L.SHOP
but I'm getting a lot of duplicates since there are many locations that belong to a single shop. I want to eliminate them and just get a list of "shop, key" entries without duplicates.
The data is correct but duplicates appear as follows:
SHOP KEY
1 XXX
1 XXX
2 YYY
3 ZZZ
3 ZZZ etc.
I would like the data to appear like this instead:
SHOP KEY
1 XXX
2 YYY
3 ZZZ etc.
SHOP table:
NO
1
2
3
LOCATION table:
LOCATION SHOP KEY
L-1 1 XXX
L-2 1 XXX
L-3 2 YYY
L-4 3 YYY
L-5 3 YYY
(ORACLE 10g Database)
You need to GROUP BY 'S.No' & 'L.KEY'
SELECT S.NO, L.KEY
FROM SHOP S
LEFT OUTER JOIN LOCATN L
ON S.NO = L.SHOP
GROUP BY S.NO, L.KEY
EDIT Following the update in your scenario
I think you should be able to do this with a simple sub query (though I haven't tested this against an Oracle database). Something like the following
UPDATE shop s
SET divnkey = (SELECT DISTINCT L.KEY FROM LOCATN L WHERE S.NO = L.SHOP)
The above will raise an error in the event of a shop being associated with locations that are in multiple divisions.
If you just want to ignore this possibility and select an arbitrary one in that event you could use
UPDATE shop s
SET divnkey = (SELECT MAX(L.KEY) FROM LOCATN L WHERE S.NO = L.SHOP)
I had this problem too but I couldn't use GROUP BY to fix it because I was also returning TEXT type fields. (Same goes for using DISTINCT).
This code gave me duplicates:
select mx.*, case isnull(ty.ty_id,0) when 0 then 'N' else 'Y' end as inuse
from master_x mx
left outer join thing_y ty on mx.rpt_id = ty.rpt_id
I fixed it by rewriting it thusly:
select mx.*,
case when exists (select 1 from thing_y ty where mx.rpt_id = ty.rpt_id) then 'Y' else 'N' end as inuse
from master_x mx
As you can see I didn't care about the data within the 2nd table (thing_y), just whether there was greater than zero matches on the rpt_id within it. (FYI: rpt_id was also not the primary key on the 1st table, master_x).