I have a relational database for a Burger Building application that a restaurant uses. Two of the tables contained in the DB are Category and Item. These are used to display the categories and then the customer can select a category (E.G. Buns) and view all of the children contained in that category and choose which ones to add to their order. The two tables are linked using a field called CategoryID.
The Item database contains amongst many, the following fields: ItemID, ItemName, TimesOrdered, CategoryID.
One of the required functions is to view the item that has been ordered the most (most popular) per category. This can be retrieved from the TimesOrdered field. However, if two items have been ordered the same amount of times, then there is technically not any item in that category that has been ordered the most.
Therefore, the largest TimesOrdered field will have to be compared to the second largest TimesOrdered field to determine if any items have been ordered the most for that category.
Is there any way to achieve this using SQL? For example, showing the ItemID for each category (using Grouping on CategoryID) that has been ordered the most as long as the item that has been ordered the second most has been ordered less times than the item that has been ordered the most.
I know that this can obviously be done by simply viewing the first two items and comparing the second record's TimesOrdered field with the first record's TimesOrdered field, but as a challenge and a way to improve my SQL, is their any way to get the desired results by using a single SQL statement?
Thanks in advance for any responses :)
Would it be possible to share some sample data? For example, what types of records are in your Item table?
How specifically is your Item table related to your Category table? Do you have multiple items per category?
I'd also want to know how the TimesOrdered field gets updated. Is this something that is updated manually by a user whenever that item is ordered, or handled by code?
Regarding the output: It sounds like you want to display, by category, the item with the most orders. Is this correct? If so, would it be displayed via a query the user runs? It sounds like you want to display something different for categories with multiple items having the "max ItemCount" for that category. If a given category has multiple items with max ItemCount, what should display for that category? Could you provide some sample output of what you're expecting to see?
I'm thinking the best way to handle this would be to use multiple sub-queries, which can get rather hairy in Access. It might be best to break this into separate queries in Access, which you can progressively select from
Create a query Q1 that shows the max TimesOrdered for each category.
Create a query Q2 that uses Q1 to figure out how many items for each category have the max TimesOrdered value.
Depending on how you want to display the final results, you could create a new query, Q3, that either shows NULL for the item in that category (if there's a tie), or the appropriate item. Basically, you'd display the item from each category where the TimesOrdered matches the max TimesOrdered for that category (having to possibly do special handling for categories with ties).
Another thing you might want to think about: What about having a separate Orders table that stores details of each order, rather than having a TimesOrdered field? Of course, that would complicate your queries further, but give you more data to report on.
Related
We are storing data for multiple stores in the same index.
We want to create facets for several fields , like category (which is hierarchical), price, color, size, price , but we want to calculate these facets per store id.
We will never have a use case - where we want to count across stores.
How do we handle this usecase , shall we add storeid as part of all the values we give to facets , or shall we declare all facets as hierarchical , and have storeid as the first level
There may be multiple ways to handle this but based on my experience I'd suggest that when you create your drill down query for your facets (to specify the level in the category hierarchy that you are interest in) and you pass that query a baseQuery, the base query should include your criteria that storeid equals a specific store.
In a sense the storeid needing to be for a specific store is just another query criteria (that you happen to be adding on behind the scenes) for indicating which products the the customer is interested in. This is not much different than if you we also specifying that only products with a specific color are of interest.
I was just after some input on database design. I have two tables, Orders and Items.
The items table is going to be a list of items that can be used on multiple orders, each item has an id
The way i thought to do it at the moment, was in the order to put an array of comma seperated ids for each item in the order.
does that sound like the best way?
also im using linq to entity framework and i dont think id be able to create a relationship between the tables, but i dont think one is needed anyway is there, since the items are not unique to an order
Thanks for any advice
The way I thought to do it at the moment, was in the order to put an array of comma separated ids for each item in the order. Does that sound like the best way?
Absolutely not - It will be MUCH more difficult in SQL to determine which orders contain a particular item, enumerate the items (to get a total, for example), and to add/remove items from an order.
A much better way would be to create an OrderItem table, which has a foreign key back to Order and Item and any other attributes relating to the item in that order - quantity, discount, comments, etc.
As far as EF goes, it will probably create a third entity (OrderItem) that will "link" the two tables. If you don't add any extra properties (which you probably should) then EF will probably create it as a many-to-many relationship between the Order and Item entities.
As far as I have understood from your question (it is not very clear), every Order can have multiple Items and every Item can be used in multiple orders. If this is what you want, you have a many to many relationship, that must be resolved using an intersection entity. This intersection entity has 2 foreign keys, one for item and one for order. Using it, you can identify what items are in a certain order and what orders need a certain item.
As my explanation is very short and very sloppy, I will recommend you the following references:
http://sd271.k12.id.us/lchs/faculty/bkeylon/Oracle/database_design/section5/dd_s05_l03.pdf
Resolve many to many relationship
Also, you proposed design is very bad, as it breaks the first normal form: no attribute can have multiple values. You shoud try to build databases at least in third normal form.
Regarding the database design, you would usually create a third table - ORDER_ITEMS - linking the two tables, containing columns (foreign keys) for order id and item id. You might also want to include a column for quantity.
I name my tables according to what the row describes. So if it describes one comment in one row, I name it "comment".
I have a table with id, created_at, updated_at, name, description, quantity, sample. I am unsure what to name it due to "quantity". I think it can be seen in two ways.
The table describes one specific kind of item. There are x number of this one kind of item. As such the table should be named "item". Similar to fish vs fishes.
The table describes many items in each row due to quantity. As such it should be named "items". The caveat is that there can be 0 or 1 of the item.
I've also entertained the idea that quantity may be describing a subtly different entity and belongs in a separate table.
Ultimately, I think this is a style thing, but I think you should be consistent across your tables rather than trying to come up with a different concept table by table.
Personally I prefer singular because of the inconsistencies of pluralizing words, but a lot of people prefer plural because the table seems to be a collection of things.
In your example, though, I'm not sure why the presence of "quantity" as one of your columns would factor in. A table called "animal" could have a "number_of_legs" column, but I don't think that would change the way you think about the overall table of animals.
Item.
Each row contains a kind of item. A property of the item is the quantity. If each specific item had a separate row, and included a column such as SerialNumber, then Items would be appropriate.
Each row is not exactly describing an item, but an item bundle, right? Either way, don't overthink it.
From your question I would use 'item' because it's gonna be more similar to your other tables.
I have a table for the "Features and benefits" of a list of products. In this table there is an item number, base part number, and three benefit columns. I want to change this to a dynamic table in which they can have any number of benefits, which I can do easily. The problem is the features and benefits do not change between items under the same base part number. For example under the base part "708" the items 708/s, 708/m and 708/l would all have the same features and benefits, so I want to get rid of the redundancy by removing the item column and just have a single entry for each distinct base part number. How would I go about this?
You might need to introduce a 'benefits grouper' field in your table, and relate that to another table with benefitsGrouperID, benefitSequence, and benefit
I have one data warehouse table that contain one row for each item sold.
Each row contains the item's type.
What MDX request could show the number of items sold for each item type?
What (dimensions,levels,etc) would it suppose to create?
In case it is relevant, I am using Pentaho/Mondrian/Spoon/Schema Workbench.
When you build a cube from the data warehouse you would typically aggregate rows for each product sale into totals for groups of one hour, or one day, per product. Few big cubes would support drilling down to individual product sales.
After creating a [Product] hierarchy/dimension you would create a virtual dimension based on that, using the item types, to give another way of breaking the information down.