I have 2 different JSON Files. One with user details and other with order details. Order details table has a column user_id to match the user ordered for. I have to create a dynamo db table that has the order details nested inside the user details and insert the values from the Json files into this table using a spring-boot app. Can someone help me with this ? Do we have any example code ?
DynamoDB is NOT a relational DB so you can't have relations per se.
However, you have two ways (at least those come to my mind) to achieve what you want.
1) Have two tables: User and Order, the latter with userId field. When you load Order, get your userId and load also a User by the index id.
2) In your User.java you can have field List<Order> orders. Then you need to create Order.java and annotate this class with #DynamoDBDocument. This enables you to have custom objects in your #DynamoDBTable classes. Do not also forget about getters and setters since they are required.
Related
Hopefully, you can help me with the following doubts that I have.
So I have an entity called User that has some columns like Nationality, Gender, Professional Status. And I have an entity for each column referred.
I'm looking for the best way to define this.
Should I apply a ManyToMany relationship between those tables? Since Users can have the same Nationality and Gender?
When I try to implement this, Spring is creating a third table automatically and I don't understand the need.
Having the following shouldn't be enough?:
Table User:
id,
name,
id_nationality.
id_gender,
id_professional_status
Table Nationality:
id,
nationality
(etc)
Why Spring is creating another table called user_nationality?
Thanks in advance.
Whenever we are using the ManyToMany relationship in that case a separate table will be created containing both primary keys of the tables involved in the new relationship.
I have two scenarios that I want to support but I don’t know the best way to design relations in the elasticsearch. I read the entire elasticsearch documentation but I couldn’t find the best way to design types for my scenarios.
Multiple one to many.
Let’s assume that I have the following tables in my relational database that I want to transfer to the elasticsearch:
Transaction table Id User1Id User2Id ….
User table Id Name
Transaction contains two references to User. As far as I know I cannot use the parent->child relation specifying two parents? I need to store transaction and user in separate types because they can be changed separately. I need to be able to search transaction through user details and return users connected with transactions. Any idea how to design such structure in the elastic search?
Many to many
Let’s assume that we have the following tables:
Order Id …
OrderLine OrderId UserId Amount …
User Id Name
Order line is always saved with the order so I thought that I can store order with order lines as a nested object relation but the user must be in the separate table. Is there any way how can I connected multiple users from order line with user type? I assume that I can use application side join but I need to retrieve order and order line always together and be able to search order by user data.
I can use grandparent and grandchildren relations but then I need to make joins in the application. Any idea how to design it in the best way?
I'm having trouble figuring out a data model for my project. I'm using Parse as the backend.
I intend to have users who are in groups, and the groups have text posts. What should be classes, and what should be rows in those classes.
I'm guessing a good way to do this would be, have a group, user, and post class.
The columns for the group class would be: GroupID, GroupName, postID, UserID
The columns for the user class would be: UserID, GroupsUserBelongsTo, user name, password, email
The columns for the post class would be: UserIDPostBelongsTo, GroupID, TextFile, TimeCreated
Is there anything I'm missing, or I should change.
You're thinking is a very SQL / rows based way and you shouldn't, this isn't SQL, it's objects and relationships.
So, your classes are fine, and the actual data is fine, but where you're using ids you should be using relationships. Post should just have a pointer to user. Perhaps, don't bother with a relationship from user to groups (you can query that using the other relationship), though you can, particularly if you will have lots of users / groups.
You may also want to consider roles to provide security for the groups.
I have 2 models, one called Employee and another one User,
Employee has one field pointing to User, one to one relationship.
My problem is that i need one query method to find the Employee that has the user with certain id. I need to find the Employee with certain User id.
I know the default query methods: .findOne, .findAll, but i need to create one, alright? how i can do that? i searched a lot but probably i am missing something. I didn't found how to do a query like that.
Thanks
I want to know how to handle mysql tables created with constraints in joomla.
for a example,
theater_table
id , name, description, image, address, tel, fax ,email
theater_facility_table
id, theater_id, facility_id
facility_table
id, name, description, image
Facility table already filled with data and id is the primary key. When creating a theater I am adding facilities to it. I created facility and theater JTables.
Do I have to create theater_facility JTable too?
Using theater Model class how I insert data to theater_facility table. I know I can insert data after theater stored successfully creating and calling storeTheaterFacility() method where it contains insert query to save required information. But I feel it can't be a good method to do so. Please help me to solve this.
Depending on how you implemented the theater - facility relationship, you can handle insering new data in different parts of your code. I mean, if for example your JTable class (the one that loads theaters) is loading/saving the theater-facilities relationship too, then the same class should delete it.
May be you can take a look at other components (for example, com_content, which relates an article to a category, or K2, where you can have multiple tags related to multiple "items"(articles)), so you can take a look on how do these components handle these kind of relationships.
Another important point you shouldn't forget is to update your facility model / table to delete records from the relationship table upon facility deleting.
I hope it helped!