This is my first question for seeking a solution to a problem. I have solved various problems from here. Thanks for these useful solutions, tips and tricks from you. I'm developing app where I need to count records from two tables. I'm using room and kotlin in android studio. I have tried following count query but the result is quite 'DOUBLE' of actual records that was being added.
the query in DAO interface is as follows..
#Query("SELECT tSubject.regular, tSubject.code, Count(tNote.id) AS countFeSe
FROM tSubject LEFT JOIN tNote ON tSubject.code = tNote.sub
WHERE tNote.std=:std AND tNote.div=:div AND tNote.sem=:sem
GROUP BY tNote.sub
ORDER BY tSubject.code ASC")
fun noteCountByStd(std: Byte, div: Byte, sem:Byte):List<SubAndCount>
I have noticed that the above was correct except one minor error in it. And finally solved the problem by changing GROUP BY tNote.sub field as follows. Now it is working as expected. You may be notice other minor changes of using DISTINCT and OUTER. Removing of those words didn't change my result.
#Query("SELECT DISTINCT tSubject.regular, tSubject.code,
Count(tNote.id) AS countFeSe
FROM tSubject LEFT OUTER JOIN tNote
ON tSubject.code = tNote.sub
WHERE tNote.std=:std AND tNote.div=:div AND tNote.sem=:sem
GROUP BY tSubject.id ORDER BY tSubject.code ASC")
fun noteCountByStd(std: Byte, div: Byte, sem:Byte):List<SubAndCount>
Related
Hei guys. I am desperately seeking help.
Please take a look at this image first.
Thanks. Now
Please look at the table below. The rightmost column REMAINING BALANCE is holding the SUM of credit_amount - debit_amount. But when I add a new amount of credit it changes in the entire column. For example, the REMAINING BALANCE column has 102500.0. If I add 500 of credit is supposed to give me 102500 + 500 = 103000 only in that specific row. 102500 will stay same in the previous row. But my problem is, it changes in the entire column.
And I have used this repository to sum the total amount of credit and subtract total amount of debit.
// Find remaining balance
#Query("SELECT SUM(b.credit_amount - b.debit_amount) FROM Mosque b")
double remainingBalance();
Thanks for your attention.
Well, it seems that you need to specify a criteria in your query, otherwise, the SQL query (or JPQL in your case) will be applied to the entire table...
I'd do something like:
#Query("SELECT SUM(b.credit_amount - b.debit_amount) FROM Mosque b where b.id =?")
double remainingBalance(int id);
Otherwise, without criteria, for each Domain Object you have, you will query the entire table. Hence, you will always get the same result. If you run this query in your Database, you will see that you will have only one result, as SUM is "summing" all your rows together.
I'm interested in getting and doing some processing on all the entities A returned by a query of the form:
SELECT * FROM A a WHERE a.id not in (select b.id from B)
Where A is a "complex" entity in the sense that it inherits (InheritanceTyped.Joined) from other entities and that several of its attributes are other entities (#OneToOne and #ManyToOne).
The query itself takes a few minutes to yield results hence my desire to execute it as few as possible.
Here are the different approaches i tried to get those A elements as efficiently as possible :
Pagination using setFirstResult/ setMaxResults
Do the job, but pretty slowly as the query seems to be executed everytime.(around 50 elements processed/sec)
Getting IDs first, A objects next
Keeping all the IDs in memory is doable, so I execute once
SELECT a.id FROM A a WHERE a.id not in (select b.id from B)
and then select a from A a WHERE a.id= :id, which goes relatively fast as the id column is indexed. This is currently the solution that is the most efficient with (around 100 elements processed/sec)
Using ScollableResults I had high hope with this solution, but it ended up being slower than other alternatives, leaving me at around 20 elements processed/sec ...
As a neophyte, I don't know what other options to investigate, or if I did something wrong in any of my attempts.
Hence my questions:
Are there (factually) other approaches to efficiently tackle this kind of problem ?
Is it normal that ScrollableResults performed so poorly ? Is there something I should have paid attention to while implementing this solution?
EDIT:
Here's the execution plan
I am trying to display volunteer information with duty and what performance is allocated.
I want to display this information. However, when I run the query, it did not gather the different date from same performance. And also availability_date is mixed up. Is it right query for it? I am not sure it is right query.
Could you give me some feedback for me?
Thanks.
Query is here.
SELECT Production.name, performance.performance_date, volunteer_duty.availability_date, customer.name "Customer volunteer", volunteer.volunteerid, membership.name "Member volunteer", membership.membershipid
FROM Customer, Membership, Volunteer, volunteer_duty, duty, performance_duty, performance, production
WHERE
Customer.customerId (+) = Membership.customerId AND
Membership.membershipId = Volunteer.membershipId AND
volunteer.volunteerid = volunteer_duty.volunteerid AND
duty.dutyid = volunteer_duty.dutyid AND
volunteer_duty.dutyId = performance_duty.dutyId AND
volunteer_duty.volunteerId = performance_duty.volunteerId AND
performance_duty.performanceId = performance.performanceId AND
Performance.productionId = production.productionId
--Added image--
Result:
The query seems reasonable, in terms of it having what appear to be the appropriate join conditions between all the tables. It's not clear to me what issue you are having with the results; it might help if you explained in more detail and/or showed a relevant subset of the data.
However, since you say there is some issue related to availability_date, my first thought is that you want to have some condition on that column, to ensure that a volunteer is available for a given duty on the date of a given performance. This might mean simply adding volunteer_duty.availability_date = performance.performance_date to the query conditions.
My more general recommendation is to start writing the query from scratch, adding one table at a time, and using ANSI join syntax. This will make it clearer which conditions are related to which joins, and if you add one table at a time hopefully you will see the point at which the results are going wrong.
For instance, I'd probably start with this:
SELECT production.name, performance.performance_date
FROM production
JOIN performance ON production.productionid = performance.productionid
If that gives results that make sense, then I would go on to add a join to performance_duty and run that query. Et cetera.
I suggest that you explicitly write JOINS, instead of using the WHERE-Syntax.
Using INNER JOINs the query you are describing, could look like:
SELECT *
FROM volunteer v
INNER JOIN volunteer_duty vd ON(v.volunteerId = vd.colunteerId)
INNER JOIN performance_duty pd ON(vd.dutyId = pd.dutyId AND vd.volunteerId = pd.colunteerId)
INNER JOIN performance p ON (pd.performanceId = p.performanceId)
I'm a Seam newbie in an already established project, so a lot of code I use is borrowed and I'm not always fully sure how things work. My problem is that I am using a query object extended from EntityQuery to back a list page with search and sort capabilities that needs to search across a many-to-many relationship and a separate many-to-one relationship which must also be used to sort. Because the many-to-many relationship has to be joined in to allow for the search capability, the query returns duplicate records for each assignment. That's not a big deal because I just added "distinct" to the ejbql and that worked fine. However, when I try to order by the other many-to-one relationship, Oracle throws an error. It appears that Oracle will not accept an order by column that is not in the select clause when using the distinct keyword http://ora-01791.ora-code.com/, and http://oraclequirks.blogspot.com/2009/04/ora-01791-not-selected-expression.html.
Here are the relationships as they are defined in the entities: [Subject m:m JobFunction] (obviously through an assignment table [Subject o:m Subject_JobFunction m:o JobFunction]), and [Subject m:o Type]. Because I need to search Subject by JobFunction, it is joined in in the ejbql which requires the distinct keyword to only return distinct Subjects to the list page. When I try to order by the Type.name (through the many-to-one relationship), the resulting query makes Oracle angry and throws the "ORA-01791: not a SELECTed expression" error. SubjectQuery code:
#Override
public String getEjbql() {
return "select subject from Subject subject left outer join subject.jobFunctions as jobFunction";
}
#Override
#SuppressWarnings("rawtypes")
public List<ValueExpression> getRestrictions() {
ValueExpression[] RESTRICTIONS = {
createValueExpression("lower(subject.name) like #{subjectQuery.prepRestriction(subjectQuery.subject.name)}"),
createValueExpression("subject.active = #{subjectQuery.active}"),
createValueExpression("subject.type.name = #{subjectQuery.typeName}"),
createValueExpression("jobFunction.name = #{subjectQuery.jobFunctionName}")
};
return Arrays.asList(RESTRICTIONS);
}
When I set the query order when a user sorts by the Type name through the front end:
"#{subjectQuery.order=='UPPER(subject.type.name) asc'}"
I get the Oracle error. If I take the distinct out of the ejbql, the sort works fine, but I get duplicate Subject records. When I add the distinct keyword the list works fine without duplicate records, but the sort throws an error. Does anyone have any suggestions about how I can restructure the ejbql to return distinct records without the distinct keyword to make the sort happy, or how to do the sort without making Oracle angry that the sort column referenced in the query is not in the select clause? I have read several places that my answer might be in the the Hibernate Criteria API, but I have no idea how to leverage it in the context of an extended EntityQuery class with what I am trying to accomplish. Please Help!
If you are adding a DISTINCT, then something is broken.
"Because the many-to-many relationship has to be joined in to allow for the search capability, the query returns duplicate records for each assignment. "
Consider the case that a person can work on many projects and a project can have many persons. There is a uniqueness of a 'person/project'. If you want a list of people that work in either project A or B (or both) then you may get
FRED/PROJ_A
BILL/PROJ_A
FRED/PROJ_B
TOM/PROJ_B
BILL/PROJ_C
If you only show the names (not the projects), you can still order by project, but you will see
FRED
BILL
FRED
TOM
BILL
If you do a DISTINCT, you can no longer order by project, because you don't know whether the FRED is the one from PROJ_A or PROJ_B or whether BILL comes before TOM (based on PROJ_A) or after TOM (based on PROJ_C).
So remove the DISTINCT and always show the column on which you are ordering (because then you'll see why the duplicates aren't actually duplicates).
I'm not sure how the generated query(ies) is(are) different, but I found an answer. I wasn't aware of the fetch command for hibernate, which fixes the need for the distinct keyword (again, not sure exactly how, maybe by subquerying?). After changing the ejbql to:
#Override
public String getEjbql() {
return "select subject from Subject subject left join fetch subject.jobFunctions jobFunction";
}
the distinct is no longer needed and therefore, Oracle does not complain about the order by column not being in the select clause. The list works as expected and the sort column works! Yay!
Predictably, I found the answer here on stackoverflow. The question was not exactly the same, but the hql syntax worked for me: HQL order by within a collection
Does anyone know of a way to do a left outer join with SubSonic 3.0 or another way to approach this problem? What I am trying to accomplish is that I have one table for departments and another table for divisions. A department can have multiple divisions. I need to display a list of departments with the divisions it contains. Getting back a collection of departments which each contain a collection of divisions would be ideal, but I would take a flattened result table too.
Using the LINQ syntax seems to be broken (I am new to LINQ though and may be using it wrong), for example this throws an ArgumentException error:
var allDepartments = from div in Division.All()
join dept in Department.All() on div.DepartmentId equals dept.Id into divdept
select divdept;
So I figured I could fall back to using the SubSonic query syntax. This code however generates an INNER JOIN instead of an OUTER JOIN:
List<Department> allDepartments = new Select()
.From<Department>()
.LeftOuterJoin<Division>(DepartmentsTable.IdColumn, DivisionsTable.DepartmentIdColumn)
.ExecuteTypedList<Department>();
Any help would be appreciated. I am not having much luck with SubSonic 3. I really enjoyed using SubSonic 2 and may go back to that if I can't figure out something as basic as a left join.
Getting back a collection of departments which each contain a collection of divisions would be ideal
SubSonic does this for you (if you setup your relationships correctly in the database), just select all Departments:
var depts = Model.Department.All();
There will be a property in each item of depts named Divisions, which contains a collection of Division objects.