I am building a SQLite database and am not sure how to proceed with this scenario.
I'll use a real-world example to explain what I need:
I have a list products that are sold by many stores in various states. Not every Store sells a particular Product at all, and those that do, may only sell it in one State or another. Most stores sell a product in most states, but not all.
For example, let's say I am trying to buy a vacuum cleaner in Hawaii. Joe's Hardware sells vacuums in 18 states, but not in Hawaii. Walmart sells vacuums in Hawaii, but not microwaves. Burger King does not sell vacuums at all, but will give me a Whopper anywhere in the US.
So if I am in Hawaii and search for a vacuum, I should only get Walmart as a result. While other stores may sell vacuums, and may sell in Hawaii, they don't do both but Walmart does.
How do I efficiently create this type of relationship in a relational database (specifically, I am currently using SQLite, but need to be able to convert to MySQL in the future).
Obviously, I would need tables for Product, Store, and State, but I am at a loss on how to create and query the appropriate join tables...
If I, for example, query a certain Product, how would I determine which Store would sell it in a particular State, keeping in mind that Walmart may not sell vacuums in Hawaii, but they do sell tea there?
I understand the basics of 1:1, 1:n, and M:n relationships in RD, but I am not sure how to handle this complexity where there is a many-to-many-to-many situation.
If you could show some SQL statements (or DDL) that demonstrates this, I would be very grateful. Thank you!
An accepted and common way is the utilisation of a table that has a column for referencing the product and another for the store. There's many names for such a table reference table, associative table mapping table to name some.
You want these to be efficient so therefore try to reference by a number which of course has to uniquely identify what it is referencing. With SQLite by default a table has a special column, normally hidden, that is such a unique number. It's the rowid and is typically the most efficient way of accessing rows as SQLite has been designed this common usage in mind.
SQLite allows you to create a column per table that is an alias of the rowid you simple provide the column followed by INTEGER PRIMARY KEY and typically you'd name the column id.
So utilising these the reference table would have a column for the product's id and another for the store's id catering for every combination of product/store.
As an example three tables are created (stores products and a reference/mapping table) the former being populated using :-
CREATE TABLE IF NOT EXISTS _products(id INTEGER PRIMARY KEY, productname TEXT, productcost REAL);
CREATE TABLE IF NOT EXISTS _stores (id INTEGER PRIMARY KEY, storename TEXT);
CREATE TABLE IF NOT EXISTS _product_store_relationships (storereference INTEGER, productreference INTEGER);
INSERT INTO _products (productname,productcost) VALUES
('thingummy',25.30),
('Sky Hook',56.90),
('Tartan Paint',100.34),
('Spirit Level Bubbles - Large', 10.43),
('Spirit Level bubbles - Small',7.77)
;
INSERT INTO _stores (storename) VALUES
('Acme'),
('Shops-R-Them'),
('Harrods'),
('X-Mart')
;
The resultant tables being :-
_product_store_relationships would be empty
Placing products into stores (for example) could be done using :-
-- Build some relationships/references/mappings
INSERT INTO _product_store_relationships VALUES
(2,2), -- Sky Hooks are in Shops-R-Them
(2,4), -- Sky Hooks in x-Mart
(1,3), -- thingummys in Harrods
(1,1), -- and Acme
(1,2), -- and Shops-R-Them
(4,4), -- Spirit Level Bubbles Large in X-Mart
(5,4), -- Spiirit Level Bubble Small in X-Mart
(3,3) -- Tartn paint in Harrods
;
The _product_store_relationships would then be :-
A query such as the following would list the products in stores sorted by store and then product :-
SELECT storename, productname, productcost FROM _stores
JOIN _product_store_relationships ON _stores.id = storereference
JOIN _products ON _product_store_relationships.productreference = _products.id
ORDER BY storename, productname
;
The resultant output being :-
This query will only list stores that have a product name that contains an s or S (as like is typically case sensitive) the output being sorted according to productcost in ASCending order, then storename, then productname:-
SELECT storename, productname, productcost FROM _stores
JOIN _product_store_relationships ON _stores.id = storereference
JOIN _products ON _product_store_relationships.productreference = _products.id
WHERE productname LIKE '%s%'
ORDER BY productcost,storename, productname
;
Output :-
Expanding the above to consider states.
2 new tables states and store_state_reference
Although no real need for a reference table (a store would only be in one state unless you consider a chain of stores to be a store, in which case this would also cope)
The SQL could be :-
CREATE TABLE IF NOT EXISTS _states (id INTEGER PRIMARY KEY, statename TEXT);
INSERT INTO _states (statename) VALUES
('Texas'),
('Ohio'),
('Alabama'),
('Queensland'),
('New South Wales')
;
CREATE TABLE IF NOT EXISTS _store_state_references (storereference, statereference);
INSERT INTO _store_state_references VALUES
(1,1),
(2,5),
(3,1),
(4,3)
;
If the following query were run :-
SELECT storename,productname,productcost,statename
FROM _stores
JOIN _store_state_references ON _stores.id = _store_state_references.storereference
JOIN _states ON _store_state_references.statereference =_states.id
JOIN _product_store_relationships ON _stores.id = _product_store_relationships.storereference
JOIN _products ON _product_store_relationships.productreference = _products.id
WHERE statename = 'Texas' AND productname = 'Sky Hook'
;
The output would be :-
Without the WHERE clause :-
make Stores-R-Them have a presence in all states :-
The following would make Stores-R-Them have a presence in all states :-
INSERT INTO _store_state_references VALUES
(2,1),(2,2),(2,3),(2,4)
;
Now the Sky Hook's in Texas results in :-
Note This just covers the basics of the topic.
You will need to create combine mapping table of product, states and stores as tbl_product_states_stores which will store mapping of products, state and store. The columns will be id, product_id, state_id, stores_id.
On my website you can purchase a trip after choosing the departure date (among the available departure dates), knowing that each departure date has a specific price attached to it.
How should I define the [departure date / price] couples from an algorithmic point of view? I suppose they can't simply be 2 fields of the Trip table / data structure, among other fields, because these 2 fields are actually a couple. What then? Should they be contained in a separate table / data structure altogether ?
Just in case I'm working with WordPress on this project.
In my opinion should be table DEPARTURE_TERMS, table PRICES and DEPARTURE_PRICES_MAPPER where You have key ID and pair ID_DEPARTURE_TERMS , ID_PRICES. Now You define all your departures terms with prices and get as
SELECT dpm.id, dt.date, pr.price FROM DEPARTURE_PRICES_MAPPER dpm
JOIN DEPARTURE_TERMS dt ON (dpm.ID_DEPARTURE_TERMS = dt.ID)
JOIN PRICES pr ON (pr.ID = dpm.id.PRICES)
WHERE dt.date >= '2014-04-12' AND dt.date <= '2014-05-11'
I am trying to rank records in power pivot table using DAX as below in MSSQL analysis service tabular model.
Example details:
I have a shop sales detail in table.
e.g.
ShopNo date sales
-----------------
1 2014-11-09 120
1 2014-11-09 130
2 2014-11-10 130
2 2014-11-10 135
In pivot table data is analyzed month and year wise.
I want to see result like
ShopNo sales rank
-----------------
2 265 1
3 250 2
Any solution is there to display statewise population automatically.
Thanks
You should be able to achieve the ranking quite easily with PowerPivot using this formula:
RankShop:=RANKX(ALL(SalesTable[ShopNo]), [Sum of sales],,,Dense)
With SalesTable being your shops sales table. If you then create a pivot table - drag ShopNo onto Rows and add new Measure (Excel 2010, in 2013 it's Calculated Field). The resulting table could then look like this:
To find out more about RANK function, I suggest this article.
In order to hide the rank value in Grand Total row, add a simple condition that puts blank values in case of grandtotals:
=IF(HASONEVALUE(SalesTable[ShopNo]), [RankShop], BLANK())
Hope this helps.
I'm trying to implement a feature whereby, apart from all the reports that I have in my system, I will allow the end user to create simple reports. (not overly complex reports that involves slicing and dicing across multiple tables with lots of logic)
The user will be able to:
1) Select a base table from a list of allowable tables (e.g., Customers)
2) Select multiple sub tables (e.g., Address table, with AddressId as the field to link Customers to Address)
3) Select the fields from the tables
4) Have basic sorting
Here's the database schema I have current, and I'm quite certain it's far from perfect, so I'm wondering what else I can improve on
AllowableTables table
This table will contain the list of tables that the user can create their custom reports against.
Id Table
----------------------------------
1 Customers
2 Address
3 Orders
4 Products
ReportTemplates table
Id Name MainTable
------------------------------------------------------------------
1 Customer Report #2 Customers
2 Customer Report #3 Customers
ReportTemplateSettings table
Id TemplateId TableName FieldName ColumnHeader ColumnWidth Sequence
-------------------------------------------------------------------------------
1 1 Customer Id Customer S/N 100 1
2 1 Customer Name Full Name 100 2
3 1 Address Address1 Address 1 100 3
I know this isn't complete, but this is what I've come up with so far. Does anyone have any links to a reference design, or have any inputs as to how I can improve this?
This needs a lot of work even though it’s relatively simple task. Here are several other columns you might want to include as well as some other details to take care of.
Store table name along with schema name or store schema name in additional column, add column for sorting and sort order
Create additional table to store child tables that will be used in the report (report id, schema name, table name, column in child table used to join tables, column in parent table used to join tables, join operator (may not be needed if it always =)
Create additional table that will store column names (report id, schema name, table name, column name, display as)
There are probably several more things that will come up after you complete this but hopefully this will get you in the right direction.
I am beginner with Ms Access and databases
I am building meeting management database. I am stuck at some point please help
Database purpose is to manage meetings with different firms which are in most cases reoccurs time to time
Table that I have created.
Table 1 - Firms
FirmID - AutoNo - PK
FirmName - Text
....
Table 2 - FirmReps (to store multiple reps of each firm)
FirmRepID - AutoNo
FirmID - FK
RepName - Text
...
Table 3 - Meeting Details (will be the main form)
MeetingID - AutoNo
MeetingDate - Date/Time
MeetingTime - Date/time
Venue - Text
FirmName - FK
...
I am looking for solution that when I enter meeting details and select the firm name all individuals will be shown in separate sub-form where I can select (tick) the interested reps for meeting
I have created a subform for FirmReps and link the master with FirmID but Every time I select the firm name all the reps are shown and not saved/linked with the meeting ID.
To get only the selected firm in the combobox on the subform, you can refer to the main form FirmID. Set the Row Source for the combo like so:
SELECT FirmRepID, RepName FROM FirmReps
WHERE FirmID = Forms!NameOfMeetingsFormHere!FirmID