I need to get data from 3 tables. However, I can only get correct results as long as there are 2 tables. As soon as I join the 3rd table, I get null results. The query that works is:
select a.first_name,a.last_name,a.email, a.birthdate,b.mobile_phone
from REGISTRATION a
left join TRIPS b on a.trip_id=b.trip_id
where a.trip_id=9 and registration_status='Active'
However, as soon as I use following query to get data from 3rd table, I get null results:
select a.first_name,a.last_name,a.email, a.birthdate,b.mobile_phone,d.country_name
from REGISTRATION a
left join TRIPS b
on a.trip_id=b.trip_id and registration_status='Active'
left join DESTINATION_COUNTRY d
on b.destination_country_id=d.destination_country_id
where a.trip_id=9
Please advice me what I am doing wrong.
Thanks a lot.
you should remove this from join "and registration_status='Active'" and move it to where clause :
select a.first_name,a.last_name,a.email, a.birthdate,b.mobile_phone,d.country_name
from REGISTRATION a
left join TRIPS b
on a.trip_id=b.trip_id
left join DESTINATION_COUNTRY d
on b.destination_country_id=d.destination_country_id
where a.trip_id=9 and registration_status='Active'
Related
I am getting issues with the below SQL query, unable to fetch the desired result
SELECT
C.Department__c
,C.Email
,R.AcctID__c
,C.ContactID__c
,R.TransactionDueDate
,R.PubNbr__c
FROM RenewalNotificationProgramDE R
LEFT JOIN ContactNewDE C
ON R.AcctID__c = C.AcctID__c
The idea is to join all the AccountID(AcctID__c) in RenewalNotificationProgramDE table to the corresponding contacts in ContactNewDE table. AccountID is the foreign key in the ContactNewDE table. I am usig Innerjoin in my query as I want all AccountID to map with their corresponding contacts in ContactNewDE.
Just replace LEFT JOIN by INNER JOIN to get all AccountID with their corresponding contacts :-
Use below query :-
SELECT
C.Department__c
,C.Email
,R.AcctID__c
,C.ContactID__c
,R.TransactionDueDate
,R.PubNbr__c
FROM RenewalNotificationProgramDE R
INNER JOIN ContactNewDE C
ON R.AcctID__c = C.AcctID__c
You have used LEFT JOIN in your query, which you need to change it to INNER JOIN. I think you would better to notice the below notes about differences between left and inner joins:
INNER JOIN: Returns all rows when there is at least one match in BOTH
tables
LEFT JOIN: Return all rows from the left table, and the
matched rows from the right table
I have two tables.
Table A:
root_id, root_text
Table B:
word_id , word_text,root_text
Now Some of the records of Table B has root_texts which might not exist in Table A.
So for that I am trying to use left join.
select *
from A a , B b
where a.root_text=+b.root_text
I only get the records which has matching root_text.
If I use the new way
Select
*
from
A left join B on a.root_text= b.root_text
I get so many extra records. I am Using MySQL 5.6.1.7
UPDATE :
http://sqlfiddle.com/#!9/7b32a/2
Query I am running
select * from word_detail w left join roots r
on r.root_text =w.root
and w.surah_no=1
and w.verse_no=1
and w.word_no=1
What I am doing wrong ?
As in result you see so many records which are not needed. The filter verse_no , word_no not working.
Update
The issue was after the left join we have to use where
select * from word_detail w left join roots r
on r.root_text =w.root
where w.surah_no=1
and w.verse_no=1
and w.word_no=1
If you want all records from TableB that are not present in table A you should use this:
Select *
from
B left join A
on a.root_text= b.root_text
where
a.root_text is null
or if you want the opposite - all records from tableA that are not present on tableB:
Select *
from
A left join B
on a.root_text= b.root_text
where
b.root_text is null
btw, this is not a left join on MySQL:
select * from A a , B b where a.root_text=+b.root_text
but will result as a simple INNER JOIN
The += operator is not standard SQL, but specific to the Oracle RDBMS, so it will not work as expected on MySQL.
The LEFT JOIN syntax is correct, the "many extra records" stem from the data in your tables. You might want to use some sort of WHERE as a filter or an aggregate to group the result set to make it more managable.
Your first example is an inner join which explains why you are not getting as many results as when you are left joining. Left joining can also be thought of as a left outer join.
Below is my sql statement
SELECT a.purchase_id,
b.username,
a.purchase_packageid,
a.purchase_tradelimit,
a.purchase_pincode,
a.purchase_datetime,
c.packages_name ,
FROM purchase a,
accounts b,
packages c
WHERE a.purchase_userid=b.UserId
AND c.packages_id=a.purchase_packageid
Basically the issue is I got 3 tables
Accounts
Purchase
Packages
The main table is Purchase, inside the table there is purchase_userid , which I need to use it to get username from table accounts
So the problem now is I got rows where the purchase_userid is blank, because its blank, it won't draw its record as null.
The only record that show in this sql statement is only those with purchase_userid,
As the value for purchase_userid will be fill up later for my web app,
I still want to select rows without purchase_userid and those with purchase_userid
Thanks for helping !!
You need to use a left join to load all records in Purchase even when no matching records are found in Accounts.
SELECT a.purchase_id, b.username, a.purchase_packageid, a.purchase_tradelimit, a.purchase_pincode, a.purchase_datetime, c.packages_name
FROM purchase a LEFT JOIN accounts b
ON a.purchase_userid=b.UserId
JOIN packages c
ON c.packages_id=a.purchase_packageid
This post explains the different kinds of joins pretty well: What's the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN?
You're using the old-timey syntax for INNER JOINs between your tables, when what you need is LEFT JOIN operations. Try this:
SELECT a.purchase_id,
b.username,
a.purchase_packageid,
a.purchase_tradelimit,
a.purchase_pincode,
a.purchase_datetime,
c.packages_name
FROM purchase AS a
LEFT JOIN accounts AS b ON a.purchase_userid = b.UserId
LEFT JOIN packages AS c ON a.purchase_packageid = c.packages_id
This works better for you because the kind of JOIN you were using suppresses records from your a table when they weren't matched in your b or c table. This LEFT JOIN will leave the a table records in place, and put NULL values where you are calling for data from the other two.
Im trying to join 3 tables together using left join.
My problem is that I dont get the right join for my query.
The number of return rows is different.
The count is not correct.
If I run this I get correct join and more than 1 row.
SELECT classes.name, trainers.trainer_name trainerName
FROM gym_classes classes
left join gym_tainer_rel trainers
on
classes.teacher = trainers.id
But If I try this query:
SELECT classes.name, trainers.trainer_name trainerName, count(usersInClass.user_name) as sum
FROM gym_classes classes
left join gym_tainer_rel trainers
on
classes.teacher = trainers.id
left join class_user_rel usersInClass
on
usersInClass.class_id = classes.id
I get only 1 row back and the count is not correct.
I am trying to select data from 3 separate tables, where 2 of those contains multiple rows of data. The sql query i am using is this, but i am experiencing that when i run it, if either taskdependees or tasksdependencies have zero result, the whole task is not showing.
SELECT t.*, GROUP_CONCAT(a.DependenciesId) as DiesId, GROUP_CONCAT(b.DependeesId) as DeesId FROM tasks t JOIN tasksdependencies a ON a.TasksId=t.TasksId JOIN taskdependees b ON b.TasksId=t.TasksId GROUP BY t.TasksId
What am I doing wrong in this query?
Use LEFT JOIN , inner join will give row if there is association is present in both tables while left will return the rows from left table even if they are not associated
SELECT t.*, GROUP_CONCAT(a.DependenciesId) as DiesId,
GROUP_CONCAT(b.DependeesId) as DeesId
FROM tasks t
LEFT JOIN tasksdependencies a ON a.TasksId=t.TasksId
LEFT JOIN taskdependees b ON b.TasksId=t.TasksId
GROUP BY t.TasksId