How to join the following tables? Or is this possible?
Column origin and destination is fk.
**tbleroute**
ID ORIGIN DESTINATION
1 1 3
2 1 2
3 3 4
**tblelocation**
ID Name
1 Bus Station
2 Market
3 Bus Station 2
4 School
For the obvious result, you need two joins. This looks like:
select r.*, lo.name as origin_name, ld.name as destination_name
from tblrouter r join
tbllocation lo
on r.origin = lo.id join
tbllocation ld
on r.destination = ld.id;
This is a situation where table aliases are needed in the from clause to distinguish the tables.
Related
i try create query with left join when i combine multiple rows into one. I try with GROUP_CONTENT function but when i try use it my db server is going down. I use MariaDB 10.3.17. I have tables like:
Games:
game_id game_name
1 Test
2 Stack
3 Other
data_developers:
dev_id dev_name
1 Electronic Arts
2 BioWare
3 2K Games
game_developers
developer_id game_id
1 1
2 1
2 3
Result i want:
game_id game_name devs
1 Test Electonics Arts, BioWare
2 Stack 2K Games
my two sql (but didnt work)
SELECT games.*, GROUP_CONCAT(data_developers.dev_name)
FROM games
LEFT JOIN game_developers ON game_developers.game_id = games.game_id
LEFT JOIN data_developers ON data_developers.dev_id = game_developers.dev_id
LIMIT 500
and second query
SELECT games.*
FROM games
LEFT JOIN game_developers ON game_developers.game_id = games.game_id
LEFT JOIN
(SELECT GROUP_CONCAT(data_developers.developer_name) as developers,
data_developers.developer_id FROM data_developers) x
ON x.developer_id = game_developers.developer_id
But of course, also dont work :(
Your query should be something like below-
SELECT A.game_id,B.Game_name,GROUP_CONCAT(C.dev_name)
FROM game_developers A
INNER JOIN Games B ON A.game_id = B.game_id
INNER JOIN data_developers C ON A.developer_id = C.dev_id
GROUP BY A.game_id,B.Game_name
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
I have following tables in my db.
Calls:
ID Name
1 Call1
2 Call2
3 Call3
Notes:
ID Name
1 Note 1
2 Note 2
Person:
ID Name
1 Andrew
PersonCalls:
ID CallID PersonID
1 1 1
2 2 1
PersonNotes:
ID NoteID PersonID
1 1 1
1 2 1
Now I need to get data from these tables according to person id. I am able to get data from 2 tables, for example Notes and PersonNotes, but I am not able to get combined data from these tables. This should be the result.
Result:
PersonID Note Call
1 Note1 Call1
1 Note2 Call2
Please suggest
Thanks
Use Join (ie: Inner Join):
select distinct p.ID as PersonID, n.Name as Note, c.Name as Call from Person p
inner join PersonCalls pc on p.ID = pc.PersonID
inner join PersonNotes pn on p.ID = pn.PersonID
inner join Calls c on pc.CallID = c.ID
inner join Notes n on pn.NoteID = n.ID
Without getting too detailed you can use a left join on dbo.calls.ID, dbo.notes.id, dbo.person.id, etc if you are using MS SQL server. Otherwise are you sure you can't just write a report?
I have two tables device and product. the device table have columns id and device.
and product table have columns id and product.
the device table is
id device
1 a
2 b
3 b
the product table is
id product
1 x
2 y
3 z
4 s
i need the result as
id device
1 a
2 b
3 b
4 null
How about something like
SELECT p.id,
d.device
FROM product p LEFT JOIN
device d ON p.id = d.id
Also, have a look at SQL SERVER – Introduction to JOINs – Basic of JOINs
try this
select p.id,d.device from products p outer join device d
on d.id=p.id
You should try this join
select p.id,d.Device
from tblDevice d
right join tblProduct p
on d.id=p.id
I have 3 tables in my database: children, families, statuslog
Every time a child is checked in or out of the database, it is updated in the statuslog. I've done this a long time ago, but I can't seem to figure out how to do it anymore. I want to create a new view that joins all 3 tables, but I only want the newest entry from statuslog (by using the highest id).
For example, statuslog looks like this:
childID researcher status id
1 Dr. A out 1
1 Dr. A in 2
1 Dr. B out 3
1 Dr. B in 4
2 Dr. C out 5
2 Dr. C in 6
3 Dr. B out 7
3 Dr. B in 8
This is what I want to do:
SELECT *
FROM children, families, statuslog
WHERE children.familyID = families.familyID AND children.childID = statuslog.childID
Obviously, this will return the children+families tuples coupled with every single log entry, but I can't remember how to only combine it with the newest log entry.
Any help would be appreciated!
Aggregate query with max(id) retrieves last ID given a childID. This is then joined to statuslog to retrieve other columns.
SELECT *
FROM children
INNER JOIN families
ON children.familyID = families.familyID
INNER JOIN
(
SELECT childID, researcher, status
FROM statuslog
INNER JOIN
(
SELECT childID, max(ID) ID
FROM statuslog
GROUP BY childID
) lastSL
ON statuslog.childID = lastSL.childid
AND statuslog.ID = lastSL.ID
) sl
ON children.childID = sl.childID
This seems to be the typical greatest-n-per-group in which the higher id is interpreted as the newest. This query should do the trick:
select * from (
select s1.* from statusLog s1
left join statusLog s2
on s1.childId = s2.childId and s1.id < s2.id
where s2.id is null
) final
join children c on c.childId = final.childId
join families f on f.familyId = c.familyId
Correct any syntactical errors.