I am trying to query data from two related objects but receiving a "Didn't understand relationship 'Case_Comment__c' in FROM part of query call" error
My query is as follows
SELECT Id,
CaseNumber,
Status, (SELECT Text__c FROM Case_Comment__c)
FROM Case
WHERE Id IN (Select Case__c from Case_Comment__c)
Case__c in Case_Comment__c equals Id in Case
If you can, you should work the other way around :
SELECT Text__c, Case__c, Case__r.CaseNumber, Case__r.Status FROM Case_Comment__c
If you really want to work with a parent-to-children relationship, you have to use the correct field :
SELECT
Id,
CaseNumber,
Status,
(SELECT Text__c FROM Case_Comments__r)
FROM
Case
WHERE
Id IN (Select Case__c from Case_Comment__c)
Notice that I changed the first Case_Comment__c to Case_Comments__r
To be sure that the field really is Case_Comments__r, you can use the workbench : in Utilities, Rest Explorer, use the URL : /services/data/v46.0/sobjects/Case/describe, look at childRelationShips and find the relationshipName
Hope this helps
Related
I have a query like this (simplified and anonymised):
SELECT
Department.id,
Department.name,
Department.manager_id,
Employee.name AS manager_name
FROM
Department
LEFT OUTER JOIN Employee
ON Department.manager_id = Employee.id;
The field Department.manager_id may be NULL. If it is non-NULL then it is guaranteed to be a valid id for precisely one row in the Employee table, so the OUTER JOIN is there just for the rows in the Department table where it is NULL.
Here is the problem: old instances of the database do not have this Department.manager_id column at all. In those cases, I would like the query to act as if the field did exist but was always NULL, so e.g. the manager_name field is returned as NULL. If the query only used the Department table then I could just use SELECT * and check for the column in my application, but the JOIN seems to make this impossible. I would prefer not to modify the database, partly so that I can load the database in read only mode. Can this be done just by clever adjustment of the query?
For completeness, here is an answer that does not require munging both possible schemas into one query (but still doesn't need you to actually do the schema migration):
Check for the schema version, and use that to determine which SELECT query to issue (i.e. with or without the manager_id column and JOIN) as a separate step. Here are a few possibilities to determine the schema version:
The ideal situation is that you already keep track of the schema by assigning version numbers to the schema and recording them in the database. Commonly this is done with either:
The user_version pragma.
A table called "Schema" or similar with one row containing the schema version number.
You can directly determine whether the column is present in the table. Two possibilities:
Use the table_info pragma to determine the list of columns in the table.
Use a simple SELECT * FROM Table LIMIT 1 and look at what columns are returned (this is probably better as it is independent of the database engine).
This seems to work:
SELECT
Dept.id,
Dept.name,
Dept.manager_id,
Employee.name AS manager_name
FROM
(SELECT *, NULL AS manager_id FROM Department) AS Dept
LEFT OUTER JOIN Employee
ON Dept.manager_id = Employee.id;
If the manager_id column is present in Department then it is used for the join, whereas if it is not then Dept.manager_id and Employee.name are both NULL.
If I swap the column order in the subquery:
(SELECT NULL AS manager_id, * FROM Department) AS Dept
then the Dept.manager_id and Employee.name are both NULL even if the Department.manager_id column exists, so it seems that Dept.manager_id refers to the first column in the Dept subquery that has that name. It would be good to find a reference in the SQLite documentation saying that this behaviour is guaranteed (or explicitly saying that it is not), but I can't find anything (e.g. in the SELECT or expression pages).
I haven't tried this with other database systems so I don't know if it will work with anything other than SQLite.
I am trying to select data based on a status which is a string. What I want is that status 'draft' comes first, so I tried this:
SELECT *
FROM c
ORDER BY c.status = "draft" ? 0:1
I get an error:
Unsupported ORDER BY clause. ORDER BY item expression could not be mapped to a document path
I checked Microsoft site and I see this:
The ORDER BY clause requires that the indexing policy include an index for the fields being sorted. The Azure Cosmos DB query runtime supports sorting against a property name and not against computed properties.
Which I guess makes what I want to do impossible with queries... How could I achieve this? Using a stored procedure?
Edit:
About stored procedure: actually, I am just thinking about this, that would mean, I need to retrieve all data before ordering, that would be bad as I take max 100 value from my database... IS there any way I can do it so I don t have to retrieve all data first? Thanks
Thanks!
ORDER BY item expression could not be mapped to a document path.
Basically, we are told we can only sort with properties of document, not derived values. c.status = "draft" ? 0:1 is derived value.
My idea:
Two parts of query sql: The first one select c.* from c where c.status ='draft',second one select c.* from c where c.status <> 'draft' order by c.status. Finally, combine them.
Or you could try to use stored procedure you mentioned in your question to process the data from the result of select * from c order by c.status. Put draft data in front of others by if-else condition.
So I currently have a database that keeps tracks of projects, project updates, and the update dates. I have a form that with a subform that displays the project name and the most recent update made to said project. It was brought to my attention however, that the most recent update to a project does not display correctly. Ex: shows the update date of 4/6/2017 but the actual update text is from 3/16/2017.
Doing some spot research, I then learned that Access does not store records in any particular order, and that the Last function does not actually give you the last record.
I am currently scouring google to find a solution but to no avail as of yet and have turned here in hopes of a solution or idea. Thank you for any insight you can provide in advance!
Other details:
tblProjects has fields
ID
Owner
Category_ID
Project_Name
Description
Resolution_Date
Priority
Resolution_Category_ID
tblUpdates has these fields:
ID
Project_ID
Update_Date
Update
there is no built-in Last function that I am aware of in Access or VBA, where exactly are you seeing that used?
if your sub-form is bound directly to tblUpdates, then you ought to be able to just sort the sub-form in descending order based on either ID or Update_date.
if you have query joining the two tables, and are only trying to get a single row returned from tblUpdates, then this would do that, assuming the ID column in tblUpdates is an autonumber. if not, just replace ORDER BY ID with ORDER BY Update_Date Desc
SELECT a.*,
(SELECT TOP 1 Update FROM tblUpdates b WHERE a.ID = b.PROJECT_ID ORDER BY ID DESC ) AS last_update
FROM tblProjects AS a;
I have a trivial issue that I can't resolve. Currently our app uses Linq to retrieve data and get a basic integer value of the row count. I can't form a query that gives back a count without a 'select i'. I don't need the select, just the count(*) response. How do I do this? Below is a sample:
return (from io in db._Owners
where io.Id == Id && io.userId == userId
join i in db._Instances on io.Id equals i.Id **select i**).Count()
;
The select i is fine - it's not actually going to be fetching any data back to the client, because the Count() call will be translated into a Count(something) call at the SQL side.
When in doubt, look at the SQL that's being generated for your query, e.g. with the DataContext.Log property.
Using the LINQ query syntax requires a select statement. There's no way around that.
That being said, the statement will get transformed into a COUNT()-based query; the select i is there only to satisfy the expression system that underlies the LINQ query providers (otherwise the type of the expression would be unknown).
Including the select will not affect the performance here because the final query will get translated into SQL. At this point it will be optimized and will be like select (*) from ......
I have the following statements in Oracle 11g:
CREATE TYPE person AS OBJECT (
name VARCHAR2(10),
age NUMBER
);
CREATE TYPE person_varray AS VARRAY(5) OF person;
CREATE TABLE people (
somePeople person_varray
)
How can i select the name value for a person i.e.
SELECT somePeople(person(name)) FROM people
Thanks
I'm pretty sure that:
What you're doing isn't what I'd be doing. It sort of completely violates relational principles, and you're going to end up with an object/type system in Oracle that you might not be able to change once it's been laid down. The best use I've seen for SQL TYPEs (not PL/SQL types) is basically being able to cast a ref cursor back for pipelined functions.
You have to unnest the collection before you can query it relationally, like so:
SELECT NAME FROM
(SELECT SP.* FROM PEOPLE P, TABLE(P.SOME_PEOPLE) SP)
That'll give you all rows, because there's nothing in your specifications (like a PERSON_ID attribute) to restrict the rows.
The Oracle Application Developer's Guide - Object Relational Features discusses all of this in much greater depth, with examples.
To insert query:-
insert into people values (
person_varray(person('Ram','24'))
);
To select :-
select * from people;
SELECT NAME FROM (SELECT SP.* FROM PEOPLE P, TABLE(P.somePeople) SP)
While inserting a row into people table use constructor of
person_varray and then the constructor
of person type for each project.
The above INSERT command
creates a single row in people table.
select somePeople from people ;
person(NAME, age)
---------------------------------------------------
person_varray(person('Ram', 1),
To update the query will be:-
update people
set somePeople =
person_varray
(
person('SaAM','23')
)