I currently have Django models like this
MyFirstObject(models.Model):
some_field = models.BooleanField(default=False)
MySecondObject(models.Model):
first_object = models.ForeignKey(MyFirstObject, db_column='firstObjectId')
Because of various issues, our data integrity is corrupt. So, I need to find instances where MyFirstObject has been deleted, but MySecondObject still has a row w a foreign key to it.
The database would look similar to:
TABLE my_first_object
id someField
1 a
2 a
3 b
TABLE my_second_object
id firstObjectId
1 1
2 3
3 4
Notice row 3 of the TABLE my_second_object has an firstObjectID that does not have a corresponding record in the my_first_object table. I want to find all instances like that.
If I was doing raw SQL, I would do
SELECT my_second_object.id, my_second_object.firstObjectId
FROM my_second_object
LEFT JOIN ON ( my_second_object.firstObjectId = my_first_object.id )
WHERE my_first_object.id IS NULL
In Djago, I am trying
MySecondObject.objects.filter(my_first_object__id__isnull=true)
But when I look at the query that results, it is doing an inner join instead of left join. Does anyone have suggestions? Thanks!
Try like this:
first_object_ids = MyFirstObject.objects.values_list('id')
get_second_objects = MySecondObject.objects.exclude(my_first_object_id__in = first_object_ids)
Related
We are facing a weird issue with Redshift and I am looking for help to debug it please. Details of the issue are following:
I have 2 tables and I am trying to perform left join as follows:
select count(*)
from abc.orders ot
left outer join abc.events e on **ot.context_id = e.context_id**
where ot.order_id = '222:102'
Above query returns ~7000 records. Looks like it is performing default join as we have only 1 record in [Orders] table with Order ID = ‘222:102’
select count(*)
from abc.orders ot
left outer join abc.events e on **ot.event_id = e.event_id**
where ot.order_id = '222:102'
Above query returns 1 record correctly. If you notice, I have just changed column for joining 2 tables. Event_ID in [Events] table is identity column but I thought I should get similar records even if I use any other column like Context_ID.
Further, I tried following query under the impression it should return all the ~7000 records as I am using default join but surprisingly it returned only 1 record.
select count(*)
from abc.orders ot
**join** abc.events e on ot.event_id = e.event_id
where ot.order_id = '222:102'
Following are the Redshift database details:
Cutdown version of table metadata:
CREATE TABLE abc.orders (
order_id character varying(30) NOT NULL ENCODE raw,
context_id integer ENCODE raw,
event_id character varying(21) NOT NULL ENCODE zstd,
FOREIGN KEY (event_id) REFERENCES events_20191014(event_id)
)
DISTSTYLE EVEN
SORTKEY ( context_id, order_id );
CREATE TABLE abc.events (
event_id character varying(21) NOT NULL ENCODE raw,
context_id integer ENCODE raw,
PRIMARY KEY (event_id)
)
DISTSTYLE ALL
SORTKEY ( context_id, event_id );
Database: Amazon Redshift cluster
I think, I am missing something essential while joining the tables. Could you please guide me in right direction?
Thank you
I have the following models struct:
class Drive(models.Model):
car_name = models.CharField(max_length=3,blank=True, null=True,choices=sp.CAR_NAMES ,help_text="The name of the car")
class DataEntity(models.Model):
parent_drive = models.ForeignKey(Drive,models.CASCADE)
type = models.IntegerField(blank=True, null=True,choices=sp.DATA_ENTITY_TYPES, help_text="The Type of the data")
And i'm trying to get all of the Drives that have DataEntity.type = 3 and DataEntity.type = 4
I tried to use the following:
query_set = Q{(AND: ('dataentity__type', 3), ('dataentity__type', 4))}
Drive.objects.filter(query_set).distinct()
but i got empty list...
I had a look on the sql statement:
SELECT ••• FROM `drive` INNER JOIN `data_entity` ON (`drive`.`id` = `data_entity`.`parent_drive_id`) WHERE (`data_entity`.`type` = 3 AND `data_entity`.`type` = 4)) subquery
The Django system put the condition inside the WHERE statement, and it cause the problem (there is no data DataEntity that contain the both types)
How can i make the right queryset in reason to get Drives that contain DataEntity.type = 3 and DataEntity.type = 4 ?
Thanks
You can try to do this:
Drive.objects.filter(dataentity__type__in=[3, 4]).distinct()
I found the solution.
When you used Q(dataentity__type=3)&Q(dataentity__type=4) the ORM system put the AND expression in the "Where" section:
SELECT ••• FROM drive` INNER JOIN data_entity ON (drive.id = data_entity.parent_drive_id) WHERE (data_entity.type = 3 AND data_entity.type = 4))
and i got 0 results since there is no dataentity that have two types.
But when i used Drive.objects.filter(Q(dataentity__type=3))&filter(Q(dataentity__type=4)).distinct()
I got the Drives that have dataentity of type 3 and also dataentity of type 4
The SQL Query:
SELECT ••• FROM `drive` INNER JOIN `data_entity` ON (`drive`.`id` = `data_entity`.`parent_drive_id`) LEFT OUTER JOIN `data_entity` T3 ON (`drive`.`id` = T3.`parent_drive_id`) WHERE (`data_entity`.`type` = 3 AND T3.`type` = 4)
I have a select list that insists on display an numeric extra value, based on an id. I didn't get this issue with another select lists.
The basic query is
select description,id
from situation
where ID = 2 and user_id = 1
UNION
select description,id
from situation
where ID = 3 OR ID = 4 and user_id = 5
The select list get an numeric value that represents the previous id from the query. I have tried with a simple query but doesn't work.
When i try it on sql command, works fine.
Anyone could help me?
I have two tables I would like to call, but I am not sure if it is possible to combine them into one query or I have to some how call 2 different queries.
Basically I have 2 tables:
1) item_table: name/id etc. + category ID
2) category_table: categoryID, categoryName, categoryParentID.
The parent categories are also inside the same table with their own name.
I would like to call on my details from item_table, as well as getting the name of the category, as well as the NAME of the parent category.
I know how to get the item_table data, plus the categoryName through an INNER JOIN. But can I use the same query to get the categoryParent's name?
If not, what would be the mist efficient way to do it? The rest of the code is in C++.
SELECT item_table.item_name, c1.name AS CatName, c2.name AS ParentCatName
FROM item_table join category_table c1 on item_table.categoryID=c1.categoryID
LEFT OUTER JOIN category_table c2 ON c2.categoryID = c1.categoryParentID
SQL Fiddle: here
I tried with normal sql query
SELECT activity_shares.id FROM `activity_shares`
INNER JOIN (SELECT `activity_id` FROM `activity_shares`
GROUP BY `activity_id`
HAVING COUNT(`activity_id`) > 1 ) dup ON activity_shares.activity_id = dup.activity_id
Which gives me record id say 10 and 11
But same query I tried to do in Doctrine query builder,
$qb3=$this->getEntityManager()->createQueryBuilder('c')
->add('select','c.id')
->add('from','MyBundleDataBundle:ActivityShare c')
->innerJoin('c.activity', 'ca')
// ->andWhere('ca.id = c.activity')
->groupBy('ca.id')
->having('count(ca.id)>1');
Edited:
$query3=$qb3->getQuery();
$query3->getResult();
Generated SQL is:
SELECT a0_.id AS id0 FROM activity_shares a0_
INNER JOIN activities a1_ ON a0_.activity_id = a1_.id
GROUP BY a1_.id HAVING count(a1_.id) > 1
Gives only 1 record that is 10.I want to get both.I'm not getting idea where I went wrong.Any idea?
My tables structure is:
ActivityShare
+-----+---------+-----+---
| Id |activity |Share| etc...
+-----+---------+-----+----
| 1 | 1 |1 |
+-----+---------+-----+---
| 2 | 1 | 2 |
+-----+---------+-----+---
Activity is foreign key to Activity table.
I want to get Id's 1 and 2
Simplified SQL
first of all let me simplify that query so it gives the same result :
SELECT id FROM `activity_shares`
GROUP BY `id`
HAVING COUNT(`activity_id`) > 1
Docrtrine QueryBuilder
If you store the id of the activty in the table like you sql suggests:
You can use the simplified SQL to build a query:
$results =$this->getEntityManager()->createQueryBuilder('c')
->add('select','c.id')
->add('from','MyBundleDataBundle:ActivityShare c')
->groupBy('c.id')
->having('count(c.activity)>1');
->getResult();
If you are using association tables ( Doctrine logic)
here you will have to use join but the count may be tricky
Solution 1
use the associative table like an entitiy ( as i see it you only need the id)
Let's say the table name is activityshare_activity
it will have two fields activity_id and activityshare_id, if you find a way to add a new column id to that table and make it Autoincrement + Primary the rest is easy :
the new entity being called ActivityShareActivity
$results =$this->getEntityManager()->createQueryBuilder('c')
->add('select','c.activityshare_id')
->add('from','MyBundleDataBundle:ActivityShareActivity c')
->groupBy('c.activityshare_id')
->having('count(c.activity_id)>1');
->getResult();
the steps to add the new identification column to make it compatible with doctrine (you need to do this once):
add the column (INT , NOT NULL) don' t put the autoincrement yet
ALTER TABLE tableName ADD id INT NOT NULL
Populate the column using a php loop like for
Modify the column to be autoincrement
ALTER TABLE tableName MODIFY id INT NOT NULL AUTO_INCREMENT
Solution2
The correction to your query
$result=$this->getEntityManager()->createQueryBuilder()
->select('c.id')
->from('MyBundleDataBundle:ActivityShare', 'c')
->innerJoin('c.activity', 'ca')
->groupBy('c.id') //note: it's c.id not ca.id
->having('count(ca.id)>1')
->getResult();
I posted this one last because i am not 100% sure of the output of having+ count but it should word just fine :)
Thanks for your answers.I finally managed to get answer
My Doctrine query is:
$subquery=$this->getEntityManager()->createQueryBuilder('as')
->add('select','a.id')
->add('from','MyBundleDataBundle:ActivityShare as')
->innerJoin('as.activity', 'a')
->groupBy('a.id')
->having('count(a.id)>1');
$query=$this->getEntityManager()->createQueryBuilder('c')
->add('select','c.id')
->add('from','ChowzterDataBundle:ActivityShare c')
->innerJoin('c.activity', 'ca');
$query->andWhere($query->expr()->in('ca.id', $subquery->getDql()))
;
$result = $query->getQuery();
print_r($result->getResult());
And SQL looks like:
SELECT a0_.id AS id0 FROM activity_shares a0_ INNER JOIN activities a1_ ON a0_.activity_id = a1_.id WHERE a1_.id IN (SELECT a2_.id FROM activity_shares a3_ INNER JOIN activities a2_ ON a3_.activity_id = a2_.id GROUP BY a2_.id HAVING count(a2_.id) > 1