Get the list for Super and sub types

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Am Having the Tables in SQL server as Super and Sub types like below. Now if i have to get list of Furnitures then how can i get the list?

Furniture table:

Id    FurnituretypeId NoofLegs
-------------------------------
1       1               4   
2       2               4

FurnitureType table:

Id     Name
-----------------
1    chair
2    cot
3    table

Chair Table:

Id    Name        CansSwing   CanDetachable      FurnitureId    
------------------------------------------------------------
1     Chair1         Y             Y                 1

Cot Table:

Id    Name        CotType      Storage   StorageType   FurnitureId
-------------------------------------------------------------------
1      Cot1       Auto           Y            Drawer       2

How can i get the entire furniture list as some of them are chair and some of them are cot. How can i join the these tables with furniture table and get the list?

Hmmm . . . union all and join?

select cc.*, f.*
from ((select Id, Name, CansSwing, CanDetachable,
              NULL as CotType, NULL as Storage, NULL as StorageType, FurnitureId 
       from chairs
      ) union all
      (select Id, Name, NULL as CansSwing, NULL as CanDetachable,
              CotType, Storage, StorageType, FurnitureId 
       from cots
      )
     ) cc join
     furniture f
     on cc.furnitureid = f.id;

How List<Object> is subtype of List<? super Number>, Here is a definition of subtype. Type X is a subtype of type Y if and only if every object or primitive of type X is also of type Y . So the question  The vertical distance that sub- or superscripted text is moved from the original baseline varies by typeface and by use. In typesetting, such types are traditionally called "superior" and "inferior" letters, figures, etc., or just "superiors" and "inferiors".

This is a classical learning problem, that's why I'm not giving you the code to solve this but all the insights you need to do so.

You have multiple approaches possible, but I'm describing two simple ones:

1) Use the UNION statement to join two separate queries one for Chair and the other for Cot, bare in mind that both SELECT have to return the same structure.

SELECT 
    a1,
    a2,
    etc..
FROM table1 a1
JOIN table2 a2 ON a1.some = a2.some
UNION
SELECT 
    a1,
    a3,
    etc..
FROM table1 a1
JOIN table3 a3 ON a1.some = a3.some

2) You can do it all in one SELECT statement using a LEFT JOIN to both tables and and in the select using COALESCE or ISNULL to get the values for one table or the other. In the WHERE condition you have to force one or the other join to be not null.

SELECT
    a1,
    COALESCE(a2,a3) as col2
FROM table1
LEFT JOIN table2 a2 ON a1.some = a2.some
LEFT JOIN table3 a3 ON a1.some = a3.some
WHERE 
    a2.some IS NOT NULL
    OR a3.some IS NOT NULL 

Tips to spot subtypes and supertypes, Adding supertypes and subtypes to your logical data model (LDM) helps I will continue to add to this list, feel free to comment and add your own ways too! The only difference between a normal list and a super-list is what happens when you post to it. With the super-list, the membership of all the sub-lists is added (recursively) and duplicates are suppressed. Other than that, the super-list is a normal list with its own archives, access control, etc.

Mapping objects into relational models takes a degree of understanding of what is possible vs. what is wise in an RDBMS. Object oriented database systems tried to go after problems like this (generally without much success) precisely because the problem statement is arguably not the right one.

Please consider just putting all of these in one table. Then use null for the fields that don't really matter for each sub-type. You will likely end up being a lot happier in the end since you can spend less time at runtime doing joins and instead just query the information you need and use indexing on the same table to find the fasted path for each query you want to run.

SELECT * FROM CombinedTable;

Java Precisely, The constraint says that type T must be a subtype of Comparable<? super T>. type in the lst parameter of binarySearch: static int binarySearch (List<? What Are Sub Types In describing the full range of each of the personality types, one needs to take into consideration the context in which the personality is operating. Each personality operates with the same motivation, but with a set of more appropriate behaviours in one-to-one or romantic situations, social situations, or in a state of self

[PDF] Subtypes, public String getProperty(String key) { return(String)get(key); } List. Object. Subtyping requires invariant generic types. Exception: super wildcard is a supertype  There are two basic components of a building. 1. Sub Structure: The part of building that is constructed below ground level. 2. Super Structure: The part of building that is above ground level. footing and plinth of a building are a part of a sub-structure.

The Data Model Toolkit: Simple Skills To Model The Real World, 143 11: Things that Are The Same But Different - Super-Type Modelling. 147 Super-type Check List. 152 Relationships Within Super/Sub-type Models. Genres and Sub-genres -- Redefining the Superhero Movie Let's talk about movie genres. Where do superhero movies fit in? Some would say that they are a sub-genre of Science fiction, or a sub-genre

[PDF] Lecture 12 Subtypes and Subclasses, Java subtypes that are not true subtypes are confusing and B is a subtype of A iff an object of B can masquerade as an object of A in any return (int)(super. The super keyword refers to the objects of immediate parent class. Before learning super keyword you must have the knowledge of inheritance in Java so that you can understand the examples given in this guide. The use of super keyword. 1) To access the data members of parent class when both parent and child class have member with same name.

Comments
  • What columns do you want from cot and chair? Do the names have to appear in one column only? Are there other common columns if the tables and if yes, should they appear only once? Or do you just want a list of the names and possibly the FurnitureID?
  • It's difficult to understand what you need. Some sample data with expected result would solve that. Will there be cots and chairs whose furniture ID is not in the furniture table? Will there be furniture ID's which are not cots or chairs? What columns do you need to see in the final result?
  • Thanks for the solutions, i tried and learnt how to handle the above example. I am learner and came across with this super and sub types problem and designed the DB according to my learning and now facing the issue of getting the list of all types. Is there any easy way to retrieve the data? Also i do have more sub types say 10 then how can we handle this? Like two different queries and after that we can combine the results OR views OR any other better solution. I have to retrieve the data and fill it to the same classes as i have my model derived as same as my table structure.
  • While this is good information, this question either falls into one of two camps - 1.) Some type of course work. 2.) Simplified example for a workplace query. They probably aren't in a position to be making design decisions in either case.
  • This is a well known problem in DB Design called Super and sub types and after going through several articles we designed the DB as shown in the example. Now we cant change the design but need to write a service which will give list of furnitures to display in UI.