I'm trying to make an unconventional join, like this:
builder.HasOne(x => x.MATERIAL_OBJ)
.WithMany()
.HasForeignKey(c => c.MATERIAL)
.HasPrincipalKey(p => p.MATERIAL_CODE);
because the data from one of my tables comes from an external source, and I need to make a join with another table by a non-PK (VARCHAR) field.
My tables are as follow:
Transits table
+---------+----------+
| ID | MATERIAL |
+---------+----------+
| 1 | ABC |
| 2 | HIJ |
+---------+----------+
Material table:
+---------------+---------------+
| MATERIAL_CODE | SUPPLIER_NAME |
+---------------+---------------+
| ABC | SUP 1 |
| DEF | SUP 2 |
+---------------+---------------+
The transits table always comes filled, and sometimes with materials we dont have avaliable. If we have the material, then the object comes filled correctly, the problem I'm facing is that whenever the material doesn't exist in the table, my odata simply doesn't work properly, breaking the return object, like so:
Is there any way to odata to return null, instead of breaking the return?
EDIT: below is the return value:
{"#odata.context":"http://MYAPI/odata/$metadata#TRANSIT(Id,MATERIAL,MATERIAL_OBJ,MATERIAL_OBJ()","value":[{"Id":12567,"MATERIAL":"REDACTED"
Also, this seems to be something with odata, as the objects are filled in the API.
I figured out that was a problem with EF Core because of the unconventional mapping I did. I decided to do a View instead and mapped that to EF.
Related
I need to create a Rails app that will show/utilize our current CRM system data. The thing is - I could just take Rails and use current DB as backend, but the table names and column names are the exact opposite Rails use.
Table names:
+-------------+----------------+--------------+
| Resource | Expected table | Actual table |
+-------------+----------------+--------------+
| Invoice | invoices | Invoice |
| InvoiceItem | invoice_items | InvItem |
+-------------+----------------+--------------+
Column names:
+-------------+-----------------+---------------+
| Property | Expected column | Actual column |
+-------------+-----------------+---------------+
| ID | id | IniId |
| Invoice ID | invoice_id | IniInvId |
+-------------+-----------------+---------------+
I figured I could use Views to:
Normalize all table names
Normalize all column names
Make it possible to not use column aliases
Make it possible to use scaffolding
But there's a big but:
Doing it on a database level, Rails will probably not be able to build SQL properly
App will probably be read-only, unless I don't use Views and create a different DB instead and sync them eventually
Those disadvantages are probably even worse when you compare it to just plain aliasing.
And so I ask - is Rails able to somehow transparently know the id column is in fact id, but is InvId in the database and vice versa? I'm talking about complete abstraction - simple aliases just don't cut it when using joins etc. as you still need to use the actual DB name.
So I have been out of the coding game for a while and recently decided to pick up rails. I have a question about the concept of Join tables in rails. Specifically:
1) why are these join tables needed in the database?
2) Why can't I just JOIN two tables on the fly like we do in SQL?
A join table allows a clean linking of association between two independent tables. Join tables reduce data duplication while making it easy to find relationships in your data later on.
E.g. if you compare a table called users:
| id | name |
-----------------
| 1 | Sara |
| 2 | John |
| 3 | Anthony |
with a table called languages:
| id| title |
----------------
| 1 | English |
| 2 | French |
| 3 | German |
| 4 | Spanish |
You can see that both truly exist as separate concepts from one another. Neither is subordinate to the other the way a single user may have many orders, (where each order row might store a unique foreign_key representing the user_id of the user that made it).
When a language can have many users, and a user can have many languages -- we need a way to join them.
We can do that by creating a join table, such as user_languages, to store every link between a user and the language(s) that they may speak. With each row containing every matchup between the pairs:
| id | user_id | language_id |
------------------------------
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 1 | 4 |
| 4 | 2 | 1 |
| 5 | 3 | 1 |
With this data we can see that Sara (user_id: 1) is trilingual, while John(user_id: 2) and Anthony(user_id: 3) only speak English.
By creating a join table in-between both tables to store the linkage, we preserve our ability to make powerful queries in relation to data on other tables. For example, with a join table separating users and languages it would now be easy to find every User that speaks English or Spanish or both.
But where join tables get even more powerful is when you add new tables. If in the future we wanted to link languages to a new table called schools, we could simply create a new join table called school_languages. Even better, we can add this join table without needing to make any changes to the languages SQL table itself.
As Rails models, the data relationship between these tables would look like this:
User --> user_languages <-- Language --> school_languages <-- School
By default every school and user would be linked to Language using the same language_id(s)
This is powerful. Because with two join tables (user_languages & school_languages) now referencing the same unique language_id, it will now be easy to write queries about how either relates. For example we could find all schools who speak the language(s) of a user, or find all users who speak the language(s) of a school. As our tables expand, we can ride the joins to find relations about pretty much anything in our data.
tl;dr: Join tables preserve relations between separate concepts, making it easy to make powerful relational queries as you add new tables.
This is not a homework question. I am trying to learn more.
I have the following entities with attributes
Manufacturer {name} //Store Manufactueres
Model {manufacturer_id, name} //Store Models
Tint {manufacturer_id, model_id, front, side, rear} //Store measurements
I have the follow data in my Tint entity. Alphabets stands for different manufacturer name and models.
Manufacturer | Model | Front | Side | Rear |
-------------+-------+-------+------+-------
A | AD | 10 | 10 | 10 |
B | AB | 10 | 10 | 10 |
A | AA | 10 | 10 | 10 |
A | AC | 10 | 10 | 10 |
B | AA | 10 | 10 | 10 |
A | AB | 10 | 10 | 10 |
When I print it out in view, I would like to have it sorted based on Manufacturer name and then Model. So the result will be as below. The name of the Manufactures will be sorted alphabetically, then Models.
Manufacturer | Model | Front | Side | Rear |
-------------+-------+-------+------+-------
A | AA | 10 | 10 | 10 |
A | AB | 10 | 10 | 10 |
A | AC | 10 | 10 | 10 |
A | AD | 10 | 10 | 10 |
B | AA | 10 | 10 | 10 |
B | AB | 10 | 10 | 10 |
I have setup the model to make sure Manufacturer and Model is a distinct pair of values.
My question is since I am referencing using manufacturer_id and model_id, how can I get the name of the Manufacturer and Model from Manufacturer and Model table.
In my tints_controller.rb, I have #tints = Tint.all.order(:manufacturer_id). However, it will only sort based on the manufacturer_id (as in numbers) instead of the name of the manufacturer.
I know that I can do it in SQL way (SELECT, FROM, WHERE) in RoR model. However, I would like to know is it possible to use ActiveRecord to sort the data based on their name.
If I understand correctly, you have 3 models, Tint, Manufacturer and Model. I am assuming you have the appropiate has_many and belongs_to associations setup correctly.
Tint.rb
belongs_to :workspace
Manufacturer.rb
has_many :models
has_many :tints, through: :models
Model.rb:
belongs_to Manufacturer
has_many :tints
You need to first join the three models together, and then order by some criteria
tints_controller.rb
#tints = Tint.joins(model: :manufacturer).order('manufacturers.name, models.name').pluck('manufacturers.name, models.name, tints.front, tints.side, tints.rear')
That will give you all tints records and they appropiate models and manufacturers.
Any time you have the id of an entity in Rails, you can easily retrieve other associated fields simply by instantiating that entity:
#manufacturer = Manufacturer.find(params[manufacturer_id])
Then it's a simple matter to retrieve any of the other fields:
#manufacturer_name = #manufacturer.name
If you need a collection of manufacturers or manufacturer names, then it's advisable to build yourself an ActiveRecord::Relation object immediately via a scoped query (as you already know). I have no idea what your criteria are, otherwise, I'd supply some sample code. I can tell you that your scoped query should include an .order clause at the end:
#manufacturers = Manufacturer.where("some_column = ?", some_criterion).order(:sort_field)
In the above example, :sort_field would be the field by you want to sort your ActiveRecord::Relation. I'm guessing in your case, it's :name.
All this having been said, if you want fancy sorted tables, you should look into the JQuery DataTables gem. DataTables can do a lot of the heavy lifting for you, and it's convenient for your users because they can then sort and resort by any column you present.
In your tints_controller.rb, instedad of
#tints = Tint.all.order(:manufacturer_id)
please write:
#tints = Tint.all.order(:manufacturer_id, :model_id)
Answer to my question:
In tints_controller.rb, I wrote
#tints = Tint.joins(:manufacturer, :model).order("manufacturers.name ASC, models.name ASC") to join the table and order them accordingly.
I tried the answer provided by #Goston above and I had an issue when I was trying edit the tints. It did not allow me to edit.
Note: Answer provided by #Goston will order them, but it broke the edit function for my case.
I have a ChunkRelationship model with a table that looks like this:
+----+---------------+----------------+---------------------+---------------------+
| id | chunk_id | chunk_partner | created_at | updated_at |
+----+---------------+----------------+---------------------+---------------------+
| 1 | 1 | 2 | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
| 2 | 2 | 1 | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
+----+---------------+----------------+---------------------+---------------------+
Both entries are foreign keys to a Chunk model. Right now, the relationship is being saved twice, once in both directions ( 2 => 1 and 1 => 2). But the relationship can be saved once, because if one ID is known then the other can be found (What is this type of table called?).
I am wondering what the Rails way of doing that would be. I was thinking of creating a before_validation callback on the ChunkRelationship model and taking the smallest number of the two and always saving that to the chunk_id column, which would allow for checking for duplicates easier before saving. But from there I'm not sure how I would retrieve them.
The intended end result would be for chunk.partners to return all the rows paired with it, no matter which column either one is in.
Perhaps you are looking for the has_many_and_belongs_to association: http://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-many-association
This should create a many-to-many relationship which I believe you are describing.
I need to do self join using Symfony 1.4/Propel 1.4. My tables/db are too big to put here but an example table is given below to replicate the issue I'm facing.
Consider following example table with example data
Table Employee
----------------------------------------
|id | name | mid |
----------------------------------------
|1 | CEO |NULL |
|2 | CTO |1 |
|3 | CFO |1 |
|4 | PM1 |2 |
|5 | TL1 |4 |
----------------------------------------
Here first column is employee, second is employee name and 3rd is manager id. mid is link to another row in same table. For example, CTO(2) reports to CEO(1) so mid in second row is 1.
I need following output:
---------------------
|ename | manager |
---------------------
|CTO | CEO |
|CFO | CEO |
|PM1 | CTO |
|TL1 | PM1 |
---------------------
The SQL query will be:
SELECT e.name,m.name
FROM employee e, employee m
WHERE e.mid=m.id
AND e.mid NOT NULL;
My problem is, how do I write same query in Symfony/Propel 1.4? I try following
$c = new Criteria();
$c->clearSelectColumns();
$c->addSelectColumn(EmployeePeer::NAME.' as ename');
$c->addSelectColumn(EmployeePeer::NAME.' as manager');
$c->setPrimaryTableName(EmployeePeer::TABLE_NAME);
$c->addJoin(EmployeePeer::MID, EmployeePeer::ID, Criteria::INNER_JOIN);
$c->add(EmployeePeer::MID, NULL, Criteria::EQUAL);
Even I know this query do not make any sense and as per my expectation, I got PropelException.
But self join is one of the common database operation and I'm sure Propel must support that. Can someone please tell how to achieve above requirements in Symfony/Propel 1.4
According to this SQLFiddle, the SQL you want to perform is:
SELECT e.name as ename, m.name as manager
FROM employee e
LEFT JOIN employee m ON e.mid = m.id WHERE e.mid IS NOT NULL;
Like YouthPark, I think addAlias is the solution and I will do something like that:
$c = new Criteria();
$c->clearSelectColumns();
$c->addSelectColumn(EmployeePeer::NAME.' as ename');
$c->addSelectColumn(EmployeePeer::NAME.' as manager');
$c->addAlias('c2', EmployeePeer::TABLE_NAME);
$c->addJoin(EmployeePeer::ID, EmployeePeer::alias('c2', EmployeePeer::MID), Criteria::LEFT_JOIN);
$c->add(EmployeePeer::MID, Criteria::ISNOTNULL);
I'm not sure about the addSelectColumn part, by the way.
Well I never tried so not sure if that help you or not but there is no other answers so you might try/further search addAlias method, if you are stuck.
$notifCrit->addAlias("A", ThreadsPeer::TABLE_NAME);
$notifCrit->add("A.father_id", ThreadsPeer::FATHER_ID."=A.father_id", Criteria::CUSTOM);
Taken from last comment of old symfony forums
Not sure but Propel 1.4 might not support self join with build in methods as it need to set alias. So you need custom query as in above example.
$c = new Criteria();
$c->addJoin(ArticlePeer::AUTHOR_ID, AuthorPeer::ID);
$c->add(AuthorPeer::NAME, 'John Doe');
$articles = ArticlePeer::doSelect($c);