I have the following two tables:
*tableA
*tableB
TableA has a 1 to many relationship with tableB and therefore TableB has a column with a foreign key for tableA
TableA will be used to create a c# class called classA which has a bool property indicating wether it has related records in TableB called HasRecords
I could create it like this:
TableA.Select(s => new ClassA {
Hasrecords = s.TableB.Any()
}
Will this create 1 query or multiple ones because of the any function? Is there another way to do this in line without triggering multiple query executions or do I have to resort to a table valued function?
Related
Requirement is as below:
Table 1 - Order(ID, orderId, sequence, reference, valueDate, date)
Table 2 - Audit(AuditId, orderId, sequence, status, updatedBy, lastUpdatedDateTime)
For each record in ORDER table, there could be one or many rows in AUDIT table.
User is given a search form where he could enter any of the search params including status from audit table.
I need a way to join these two tables with dynamic where clause and get the top row for a given ORDER from AUDIT table.
Something like below:
select * from
ORDER t1, AUDIT t2
where t1.orderid = t2.orderId
and t1.sequence = t2.sequence
and t2.status = <userProvidedStatusIfAny>
and t2.lastUpdatedDateTime in (select max(t3.lastUpdatedDateTime) --getting latest record
AUDIT t3 where t1.orderid = t3.orderId
and t1.sequence = t3.sequence)
and t1.valudeDate = <userProvidedDataIfAny> ..... so on
Please help
-I cant do this with #Query because i have to form dynamic where clause
-#OneToMany fetches all the records in audit table for given orderId and sequence
-#Formula in ORDER table works but for only one column in select. i need multiple values from AUDIT table
Please help
I'm using Oracle12c
I have a table with a primary key and separate column.
create tableB(
ID number(10)
,data number(10)
);
ID is my primary key.
I have to join 3 tables on my query and the performance issue is the B.data without an index.
B.data contains 'null' values and multiple entries on the same numbers.
select A.examp from tabled D
join tableb B on D.data = B.data
join tablec C on B.ID = C.ID
join tablea A on C.val = A.val
where D.ID = :value;
So my question is what is the difference between an index that contains only one value like the data column
create index ind_tableb on tableb (data);
and an index that contains multiple columns like
create index ind_tableb on tableb (data, id);
Can i get an improvement by selecting the id in the index with the data in the way i join the columns ?
Thanks for any advise and help.
For this particular query, you want the two column index version:
create index ind_tableb on tableb (data, id);
The above index, if used, would let Oracle rapidly lookup tabled.data values for a potential match with a tableb.data value. If a match be found, then the same index would also contain the tableb.ID value for the next join to tablec. If you just used the single column version on tableb.data alone, then Oracle would have to seek back to the tableb table to find the ID values. This could hurt performance and might even cause the index to not be used.
$data['establishments2'] = Establishments::Join("establishment_categories",'establishment_categories.establishment_id','=','establishments.id')->where('establishments.city','LIKE',$location)->where('establishments.status',0)->whereIn('establishment_id',array($est_data))->get(array('establishments.*'));
this is controller condition.
I have two tables, in table1 i am matching id with table2 and then fetching data from table1, and in table2 i have multiple values of same id in table 1. i want to get data of table1 values only one time, but as i am hvg multiple data of same id in table2 , data is repeating multiple times, can anyone please tell me how to get data only one time wheater table2 having single value or multiple value of same id... thank you
you can do it by selecting the field name you desired
instead get all field from table establishments
$data['establishments2'] = Establishments::Join("establishment_categories",'establishment_categories.establishment_id','=','establishments.id')->where('establishments.city','LIKE',$location)->where('establishments.status',0)->whereIn('establishment_id',array($est_data))->get(array('establishments.*'));
you can select specific field from table establishments like
$data['establishments2'] = Establishments::Join("establishment_categories",'establishment_categories.establishment_id','=','establishments.id')->where('establishments.city','LIKE',$location)->where('establishments.status',0)->whereIn('establishment_id',array($est_data))->get('establishments.fieldName');
or you can also do
$data['establishments2'] = `Establishments::Join("establishment_categories",'establishment_categories.establishment_id','=','establishments.id')->where('establishments.city','LIKE',$location)->where('establishments.status',0)->whereIn('establishment_id',array($est_data))->select('establishments.fieldName')->get();`
I am new to Oracle, so kindly bear with me if the question sounds really naive.
So, I have two tables TableA and TableB which have say just two columns id, name for simplicity.
I now want to now get the id value for a particular value of name in TableA. If this would be the only requirement, this query would suffice -
SELECT id from TableA WHERE name = 'some_name';
Now, what I want to do is take this id and delete all the rows in TableB that match this id-
DELETE FROM TableB WHERE id = <id obtained from the above query>;
What is the composite query in oracle that would perform this function?
Thanks!
If you know that only a single id value is going to be returned for a particular name value, you'd just do
DELETE FROM tableB b
WHERE b.id = (SELECT a.id
FROM tableA a
WHERE a.name = 'some_name')
Note that the aliases are optional. However, adding aliases generally makes things clearer so no one has to guess which id or which name you're referring to at any point.
If there might be multiple id values in tableA for a given name, you'd just use an IN rather than an =
DELETE FROM tableB b
WHERE b.id IN (SELECT a.id
FROM tableA a
WHERE a.name = 'some_name')
This would also work if you knew that the query against tableA was only going to return one row. I'd prefer the equality query if you're sure that only one row would be returned, though. I'd generally rather get an error if my expectations were violated rather than potentially having unexpected rows get deleted.
If table Employee has foreign key for table person, department,
when get the entity of employee, I want to both associated entities loaded too.
how to write the linq query? like below?
var employee = this.Context.Employee.Include("Person, Department");
It seems not working.
var employee = this.Context.Employee.Include("Person").Include("Department");