Most specifically, I'm having trouble returning from LibreOffice Base [HSQLdb] a list of grades organized by (1) class, (2) assignment, (3) student's last name.
I want this output so I can run a script to copy the grades from the database to an online gradebook (which doesn't have an API [sadface])
I suspect several possible causes for this problem:
My relational structure may need tweaking.
I somehow need to implement a "student ID." On Zaption, Students make their submissions under whatever "ZaptionName" they choose to use. I then manually match ZaptionName to RosterFullName in the second table shown.
Zaption allows multiple submissions by the same "student" for the same assignment. Because multiple submissions are allowed, I run a FilterLowMultiples query to select the highest grade for that assignment for that student.
FilterLowMultiples:
SELECT MAX( "Grade" ) "Grade", "RosterFullName",
"Assignment", MAX( "ZaptionName" ) "ZapName"
FROM "SelectAssignment"
GROUP BY "RosterFullName", "Assignment"
SelectAssignment is below for reference:
SELECT "GradedAssignments"."Assignment", "Roster"."RosterFullName",
"GradedAssignments"."Grade", "ZaptionNames"."ZaptionName"
FROM "Roster", "ClassIndex", "GradedAssignments", "ZaptionNames"
WHERE "Roster"."Class" = "ClassIndex"."Class"
AND "GradedAssignments"."ZaptionName" = "ZaptionNames"."ZaptionName"
AND "ZaptionNames"."RosterFullName" = "Roster"."RosterFullName"
AND ( "GradedAssignments"."Assignment" = 'YouKnowWhatever')
My query to PullAssignmentGrades is as follows, but sorting by assignment fails, as there is no assignment by default unless that student submitted one, so the row is blank and that student falls to the bottom of the sort, which is bad for the transfer-to-online script I run.
SELECT "Roster"."RosterFirstName", "ClassIndex"."Class",
"Roster"."RosterFullName", "ClassIndex"."ClassLevel",
"FilterLowMultiples"."Grade", "FilterLowMultiples"."ZapName",
"FilterLowMultiples"."Assignment", "FilterLowMultiples"."Grade",
"FilterLowMultiples"."Assignment", "ClassIndex"."ClassDisplayOrder",
"Roster"."RosterLastName"
FROM "ClassIndex", "FilterLowMultiples", "Roster"
ORDER BY "Roster"."RosterFirstName" ASC,
"FilterLowMultiples"."Grade" DESC,
"FilterLowMultiples"."Assignment" ASC,
"ClassIndex"."ClassDisplayOrder" ASC,
"Roster"."RosterLastName" ASC
Use a LEFT JOIN in your query for SelectAssignment so you don't drop students who didn't do a particular assignment. Optionally you can use COALESCE on the potentially NULL values from the "GradedAssignments" table to assign a grade of 0 or I. Like so:
SELECT 'YouKnowWhatever' AS "Assignment", "Roster"."RosterFullName",
COALESCE("GradedAssignments"."Grade",0), "ZaptionNames"."ZaptionName"
FROM "Roster"
INNER JOIN "ClassIndex" ON "Roster"."Class" = "ClassIndex"."Class"
INNER JOIN "ZaptionNames" ON "ZaptionNames"."RosterFullName" = "Roster"."RosterFullName"
LEFT JOIN "GradedAssignments" ON ("GradedAssignments"."ZaptionName" = "ZaptionNames"."ZaptionName"
AND "GradedAssignments"."Assignment" = 'YouKnowWhatever')
Related
I'm trying to avoid using extra() here, but haven't found a way to get the results I want using Django's other queryset methods.
My models relationships are as follows:
Model: Enrollment
FK to Course
FK to User
FK to Mentor (can be NULL)
Model: Course
FK to CourseType
In a single query: given a User, I'm trying to get all of the CourseTypes they have access to. A User has access to a CourseType if they have an Enrollment with both a Course of that CourseType AND an existing Mentor.
This user has 2 Enrollments: one in a Course for CourseType ID 6, and the other for a Course for CourseType ID 7, but her enrollment for CourseType ID 7 does not have a mentor, so she does not have access to CourseType ID 7.
user = User.objects.get(pk=123)
This works fine: Get all of the CourseTypes that the user has enrollments for, but don't (yet) query for the mentor requirement:
In [28]: CourseType.objects.filter(course__enrollment__user=user).values('pk')
Out[28]: [{'pk': 6L}, {'pk': 7L}]
This does not give me the result I want: Excluding enrollments with NULL mentor values. I want it to return only ID 6 since that is the only enrollment with a mentor, but it returns an empty queryset:
In [29]: CourseType.objects.filter(course__enrollment__user=user).exclude(course__enrollment__mentor=None).values('pk')
Out[29]: []
Here's the generated SQL for the last queryset that isn't returning what I want it to:
SELECT `courses_coursetype`.`id` FROM `courses_coursetype` INNER JOIN `courses_course` ON ( `courses_coursetype`.`id` = `courses_course`.`course_type_id` ) INNER JOIN `store_enrollment` ON ( `courses_course`.`id` = `store_enrollment`.`course_id` ) WHERE (`store_enrollment`.`user_id` = 3877 AND NOT (`courses_coursetype`.`id` IN (SELECT U0.`id` AS `id` FROM `courses_coursetype` U0 LEFT OUTER JOIN `courses_course` U1 ON ( U0.`id` = U1.`course_type_id` ) LEFT OUTER JOIN `store_enrollment` U2 ON ( U1.`id` = U2.`course_id` ) WHERE U2.`mentor_id` IS NULL)))
The problem, it seems, is that in implementing the exclude(), Django is creating a subquery which is excluding more rows than I want excluded.
To get the desired results, I had to use extra() to explicitly exclude NULL Mentor values in the WHERE clause:
In [36]: CourseType.objects.filter(course__enrollment__user=user).extra(where=['store_enrollment.mentor_id IS NOT NULL']).values('pk')
Out[36]: [{'pk': 6L}]
Is there a way to get this result without using extra()? If not, should I file a ticket with Django per the docs? I looked at the existing tickets and searched for this issue but unfortunately came up short.
I'm using Django 1.7.10 with MySQL.
Thanks!
Try using isnull.
CourseType.objects.filter(
course__enrollment__user=user,
course__enrollment__mentor__isnull=False,
).values('pk')
Instead of exclude() you can create complex queries using Q(), or in your case ~Q():
filter_q = Q(course__enrollment__user=user) | ~Q(course__enrollment__mentor=None)
CourseType.objects.filter(filter_q).values('pk')
This might lead to a different SQL statement.
See docs:
https://docs.djangoproject.com/en/3.2/topics/db/queries/#complex-lookups-with-q-objects
I have made a few relations to do with a banking database system.
this is my current code. The table has
SELECT COUNT(AccountType) AS Student_Total FROM Account
WHERE AccountType ='Student'
and SortCode = 00000001;
SELECT COUNT(AccountType) AS Student_Total FROM Account
WHERE AccountType ='Student'
and SortCode = 00000002;
SELECT COUNT(AccountType) AS Student_Total FROM Account
WHERE AccountType ='Student'
and SortCode = 00000003;
the rest of the code is a duplicate of this part with the next type of 'Account' and looping back through sortcode's 1-3 again.
I was wondering if there was a more elegant way of producing this. I need to count the number of student, current and saver accounts for each bank.
Or is there a way to combine lots of selects together to make a neat table?
That's what GROUP BY is for!
SELECT SortCode,COUNT(AccountType) AS Student_Total FROM Account
WHERE AccountType ='Student'
GROUP BY SortCode;
UPDATE:
You can also GROUP BY with multiple grouping fields:
SELECT SortCode,AccountType,COUNT(AccountType) AS Student_Total FROM Account
GROUP BY SortCode,AccountType;
You could also apply a PIVOT approach to this query to always return a single row and know the fixed-final columns of the result set. However, applying a group by allows for more flexibility of returned rows, especially if you have a large amount of individual things you are trying to tally up.
select
A.AccountType,
SUM( IF( A.SortCode = 1, 1, 0 )) as SortCode1Cnt,
SUM( IF( A.SortCode = 2, 1, 0 )) as SortCode2Cnt,
SUM( IF( A.SortCode = 3, 1, 0 )) as SortCode3Cnt
from
Account A
where
A.AccountType = 'Student'
AND A.SortCode IN ( 1, 2, 3 )
group by
A.AccountType
Note... it appears your sort code is a numeric as you have no quotes around indicating a character string. So, all the leading zeros are irrelevant. And if you were only doing based on a single Account Type, you don't even need the leading Account Type column and can remove the group by too.
dont blame for the database design.I am not its database architect. I am the one who has to use it in current situation
I hope this will be understandable.
I have 3 tables containing following data with no foreign key relationship b/w them:
groups
groupId groupName
1 Admin
2 Editor
3 Subscriber
preveleges
groupId roles
1 1,2
2 2,3
3 1
roles
roleId roleTitle
1 add
2 edit
Query:
SELECT roles
from groups
LEFT JOIN preveleges ON (groups.groupId=preveleges.groupId)
returns specific result i.e roles.
Problem: I wanted to show roleTitle instead of roles in the above query.
I am confused how to relate table roles with this query and returns required result
I know it is feasible with coding but i want in SQL.Any suggestion will be appreciated.
SELECT g.groupName,
GROUP_CONCAT(r.roleTitle
ORDER BY FIND_IN_SET(r.roleId, p.roles))
AS RoleTitles
FROM groups AS g
LEFT JOIN preveleges AS p
ON g.groupId = p.groupId
LEFT JOIN roles AS r
ON FIND_IN_SET(r.roleId, p.roles)
GROUP BY g.groupName ;
Tested at: SQL-FIDDLE
I would change the data structure it self. Since It's not normalised, there are multiple elements in a single column.
But it is possible with SQL, if for some (valid) reason you can't change the DB.
A simple "static" solution:
SELECT REPLACE(REPLACE(roles, '1', 'add'), '2', 'edit') from groups
LEFT JOIN preveleges ON(groups.groupId=preveleges.groupId)
A more complex but still ugly solution:
CREATE FUNCTION ReplaceRoleIDWithName (#StringIds VARCHAR(50))
RETURNS VARCHAR(50)
AS
BEGIN
DECLARE #RoleNames VARCHAR(50)
SET #RoleNames = #StringIds
SELECT #RoleNames = REPLACE(#RoleNames, CAST(RoleId AS VARCHAR(50)), roleTitle)
FROM roles
RETURN #RoleNames
END
And then use the function in the query
SELECT ReplaceRoleIDWithName(roles) from groups
LEFT JOIN preveleges ON(groups.groupId=preveleges.groupId)
It is possible without function, but this is more readable. Made without editor so it's not tested in anyway.
You also tagged the question with PostgreSQL and it's actually quite easy with Postgres to work around this broken design:
SELECT grp.groupname, r.roletitle
FROM groups grp
join (
select groupid, cast(regexp_split_to_table(roles, ',') as integer) as role_id
from privileges
) as privs on privs.groupid = grp.groupid
join roles r on r.roleid = privs.role_id;
SQLFiddle: http://sqlfiddle.com/#!12/5e87b/1
(Note that I changed the incorrectly spelled name preveleges to the correct spelling privileges)
But you should really, really re-design your data model!
Fixing your design also enables you to define foreign key constraints and validate the input. In your current model, the application would probably break (just as my query would), if someone inserted the value 'one,two,three' into the roles table.
Edit
To complete the picture, using Postgres's array handling the above could be slightly simplified using a similar approach as MySQL's find_in_set()
select grp.groupname, r.roletitle
from groups grp
join privileges privs on grp.groupid = privs.groupid
join roles r on r.roleid::text = any (string_to_array(privs.roles, ','))
In both cases if all role titles should be shown as a comma separated list, the string_agg() function could be used (which is equivalent to MySQL's group_concat()
select grp.groupname, string_agg(r.roletitle, ',')
from groups grp
join privileges privs on grp.groupid = privs.groupid
join roles r on r.roleid::text = any (string_to_array(privs.roles, ','))
group by grp.groupname
I'm stuggling to replicate a SQL query into LINQ.
Can any one help?
SQL:
SELECT tblInvoice.lngID AS InvoiceID,
tblInvoice.dtTimeStamp AS InvoiceDate,
tblInvoice.strReference,
tblInvoice.fltTotalValue,
max(Project.ProjectID) AS ProjectID,
max(Project.ProjectName) AS ProjectName,
max(Project.Location) AS ProjectLocation
FROM tblInvoice INNER JOIN
tblInvoiceLine ON tblInvoice.lngID = tblInvoiceLine.lngInvoiceID
WHERE (tblInvoice.intStatus != 0)
AND (tblInvoice.lngPersonID = #PersonID)
GROUP BY tblInvoice.lngID, tblInvoice.dtTimeStamp, strReference, fltTotalValue
ORDER BY tblInvoice.lngID DESC
LINQ so far:
var invoices = from inv in db.TblInvoices
join invLine in db.TblInvoiceLines on inv.LngID equals invLine.LngInvoiceID
where inv.IntStatus != 0
where inv.LngPersonID == personID
group inv by new {inv.LngID,inv.DtTimeStamp,inv.StrReference,inv.FltTotalValue} into newInv
Part of the problem is that I want to do a
select new Invoice(){
}
and build up my custom Invoice object but, I cant see any of the properties in newInv.
Can any one advise?
I don't have time for a full answer now, but:
To get at properties of the key, use newInv.Key.StrReference etc
To get at aggregates (e.g. max values) use newInv.Max(x => x.ProjectId) etc
Hopefully that'll be enough to get you going. Basically, newInv will be a group of entries, with an associated key (which is what you grouped by).
I've got 3 dataset objects that are nested with each other using entity set objects. I am selecting the data like this
var newList = from s in MainTable
from a in s.SubTable1 where a.ColumnX = "value"
from b in a.Detail where b.Name = "searchValue"
select new {
ID = s.ID,
Company = a.CompanyName,
Name = b.Name,
Date = s.DueDate
Colour = b.Colour,
Town = a.Town
};
and this works fine, but the trouble is there are many records in the Detail object-list/table for each Name value so I get a load of duplicate rows and thus I only want to display one record per b.Name. I have tried putting
group s by b.Name into g
before the select, but then this seems to stop the select enabling me to select the columns I want (there are more, in practice). How do I use the group command in this circumstance while still keeping the output rows in a "flat" format?
Appending comment as answer to close question:-
Of course that if you group your results, you cant get select a column of a child, thats because there may be more than one childs and you have to specify an aggregate column for example the sum,max etx –