I am managing versions in my Application. I have made table name "Version". There are three separate column for "Major", "Minor" and "Bug". My version number are stored in table like this:
Id | Major | Minor | Bug | No
1 | 1 | 0 | 0 | 1.0.0
2 | 1 | 1 | 3 | 1.1.3
3 | 2 | 0 | 4 | 2.0.4
4 | 3 | 0 | 1 | 3.0.1
Here my max version should be 3.0.1 as it is highest in current scenario. I am unable to get this max record. My project is in .Net Core 3.0 and i am using entity framework core.
What i tried so far !
I was concatenating each version number like 1.0.0, 1.1.3 and so on, then i was getting list order by descending and was getting first or default. It was working good but for only single digits. When i try it on double digits it was not working.
var model =await DbSet.OrderByDescending(x => x.No).FirstOrDefaultAsync();
Can't you just order on multiple columns?
var model = await DbSet.OrderByDescending(x => x.Major).ThenByDescending(x => x.Minor).ThenByDescending(x => x.Bug).FirstOrDefaultAsync();
Related
My requirement is to calculate based on an incremental size window for a batch table.
For example, the first window has 1 row, the second window has 2 rows(including 1 row from the 1st window and a new row), then 3 rows in the 3rd window(including 2 rows from the 2nd window and a new row), and so on.
For example:
Source table:
datetime | productId | price |
3-1 | p1 | 10 |
3-2 | p1 | 20 |
3-3 | p1 | 30 |
3-4 | p1 | 40 |
Result table:
datetime | productId | average|
3-1 | p1 | 10/1 |
3-2 | p1 | (10+20)/2 |
3-3 | p1 | (10+20+30)/3 |
3-4 | p1 | (10+20+30+40)/4 |
I am trying to find a way to implement this requirement with Sql, to me seems the OVER action can do that but not yet implemented in flink, so I need an alternative way.
BTW:
I tried to use a TUMBLE window of 1 day and store the previous value in the user defined aggregation object but failed as the aggregation object will be reused by all product not a single object for each product
The OVER clause on a batch table is not supported by Flink's SQL yet. You can track the status of this effort here.
However, did you consider to implement this behavior on a streaming table instead? Streaming tables can also read from static files such as CSV files and many operations are supported there as well. This depends on the other operations you want to use in your query, though.
I have a super-class/subclass hierarchical relationship as follows:
Super-class: IT Specialist
Sub-classes: Databases, Java, UNIX, PHP
Given that each instance of a super-class may not be a member of a subclass and a super-class instance may be a member of two or more sub-classes, how would I go about implementing this system?
I haven't been given any attributes to assign to the entities so I find this very vague and I'm at a loss where to start.
To get started, you would have one table that contains all of your super-classes (in your example case, there would only be IT Specialist, but it could also contain things like Networking Specialist, or Digital Specialist). I've included these to give a bit more flavour:
ID | Name |
-----------------------------
1 | IT Specialist |
2 | Networking Specialist |
3 | Digital Specialist |
You also would have another table that contains all of your sub-classes:
ID | Name |
--------------------
1 | Databases |
2 | Java |
3 | UNIX |
4 | PHP |
For example, let's say that a Networking Specialist needs to know about Databases, and a Digital Specialist needs to know about both Java and PHP. An IT Specialist would need to know all four fields listed above.
There are two possible ways to go about this. One such way would be to set 'flags' in the sub-class table:
ID | Name | Is_IT | Is_Networking | Is_Digital
----------------------------------------------------
1 | Databases | 1 | 1 | 0
2 | Java | 1 | 0 | 1
3 | UNIX | 1 | 0 | 0
4 | PHP | 1 | 0 | 1
Keep in mind, this is only using a small number of skills. If you started to have a lot of super-classes, the columns in the sub-class table could get out of hand pretty quickly.
Fortunately, you can also use something known as a bridging table (also known as an associative entity). Essentially, a bridging table allows you to have two foreign keys that are primary keys in another table, solving the problem of a many-to-many relationship.
You would set this up by having a new table that associates which sub-classes belong with which super-classes:
ID | Sub-class ID | Super-class ID |
-------------------------------------
1 | 1 | 1 |
2 | 1 | 2 |
3 | 2 | 1 |
4 | 2 | 3 |
5 | 3 | 1 |
6 | 4 | 1 |
7 | 4 | 3 |
Note that there are 'duplicates' in both the sub-class ID and super-class ID fields, yet no duplicates in the ID field. This is because the bridging table has unique IDs, which it uses to make independent associations. Sub-class 1 (Databases) needs to be associated to two different groups (IT Specialist and Networking Specialist). Thus, two different associations need to be formed.
Both approaches above give the same 'result'. The only real difference here is that a bridging table will give you more rows, while setting multiple flags will give you more columns. Obviously, the way in which you craft your query will be different as well.
Which of the two approaches you choose to go with really depends on how much data you're dealing with, and how much scope the database is going to have for expansion in the future :)
Hope this helps! :)
I'm working with Microsoft SQL Server Report Builder 3.0. I ran into a problem I can't solve myself.
I've got the following table:
ID | price
----------
0 | 5
1 | 10
2 | 7
3 | 9
4 | 6
What I want to do is to subtract the price from ID 0, from every other ID.
The result should look similar to this:
ID | price
----------
0 | 0
1 | 5
2 | 2
3 | 4
4 | 1
I think "lookup" could do the job, I just can't get it to work.
I tried:
=Fields!price.Value-Lookup(0,Fields!ID.Value,Fields!price.Value, "DataSet1")
Is there any way to get to this result?
(In C# I would use a Dictionary and do something like for(...){ID[i]-ID[0]} If that helps to explain what I mean)
I think I found a solution:
Sum(iif(Fields!ID.Value=0,Fields!price.Value,0),"DataSet1")
This should give the correct result, but Im not sure if it works everytime.
Is there another (better) way to do this?
Not sure if it works exactly as expected but should give you an idea on one use for RunningValue
= Fields!price.Value - RunningValue(iif(Fields|ID.Value = 0 ,Fields!price.Value,0), Sum, "DataSet1")
I would like to check whether
if there any ways to delete the record in the page, without deleting records in database?
I'm doing a shopping cart and would like to have the user to be able to view back their past transaction.
Is there any ways that I could delete the records in the cart, after I check out? And also able to view the past transaction.
I've not done any code yet,
just seeking for advices
Yes. You can have a database with the products, a second with your users and a third one to associate the users id with the products id they purchased.
You can never delete a item from the database. You can include a information of status like 'active/inactive' instead of actually deleting it.
Edit
When you have products in cart, usually the list is saved in cookies, temporarily by browser or javascript or another way (if your country forbid cookie, you have to search for alternatives). Once the purchase is finished, the cart list is saved in database and the cookie or whatever is cleared. You do not delete anything from database.
Example
Users/ buyers database
+--------+----------+
| idUser | nameUser |
+--------+----------+
| 1 | Antony |
| 2 | Betty |
| 3 | Carl |
+--------+----------+
Products database
+-----------+--------------+-------+-----------+
| idProduct | nameProduct | price | available |
+-----------+--------------+-------+-----------+
| 1 | Apple dozen | 10.00 | yes |
| 2 | Banana unity | 20.00 | yes |
| 3 | Cherry kg | 30.00 | yes |
+-----------+--------------+-------+-----------+
Active/ Inactive Example
Notice here how you don't need to delete any record ever. You can create a option such like available to products like example above. So you can just set it to yes or no. So you just code your front-end to show products which available is yes while your back-end can see all of them. It is very useful. In a case when your product has tens of information and you delete the product, but it will only be unavailable for 3 weeks, you would lose a great time deleting and typing and saving everything again. It is much better just set it to show or not to show. (Some stores just opt to show everything, but alert when it is unavailable).
Have in mind that it isn't a rule for everything. Always look for the best perfomance. If you have a database with 10k unavaiable products that will never be available again and you just have 2 available itens, it would be a little nosense keep all this records alive.
About prices historic
Prices Historic Database
+--------+--------+-----------+-----+----------+----------+
| idItem | idUser | idProduct | qty | subtotal | date |
+--------+--------+-----------+-----+----------+----------+
| 1 | 1 | 1 | 2 | 20 | 10/10/13 |
| 2 | 1 | 2 | 1 | 20 | 10/10/13 |
| 3 | 2 | 1 | 1 | 10 | 11/12/13 |
| 4 | 2 | 2 | 1 | 20 | 11/12/13 |
| 5 | 2 | 3 | 1 | 30 | 11/12/13 |
| 6 | 1 | 1 | 1 | 10 | 01/06/14 |
+--------+--------+-----------+-----+----------+----------+
It is always good to have a unique identification for each row on database. Well, in most cases. Its is not very readable for humans, but it fits well for machines. Check this database. The line 1 and 2 say us that user 1 bought on 10/10/13 the item with id 1 x 2 and item with id 2 x 1. Translating: Antony bought 2 Apple dozen and 1 Banana unity.
In this database you could filter rows by user and them group by Date. You would see that Antony bought more Apples in 01/06/2014.
I personally like to save the subtotal on database. If in 2015 the apple price raise to 15.00, you and the user can see he paid 10.00 in 2013 and you can do reverse calc to get the individual price.
If you could read this thid database well, you see Betty bought one of each item in 11/12/13 and Carl has never bought anything.
I believe and hope it will help you.
It is just a simplified example on how the logic works. I matched the product directly with buyer, but most stores usually add a 4th database just to list Orders. So you relate Users with Orders and Orders with Products. Everything has its advantages and disadvantages
I met some problems with creating table using Extjs. My table has difficult structure
-------------------------------------------|
| | | 4 |
| | 2 ---------|
| | | 5 |
| 1 |---------------------------|
| | | 6 |
| | 3 ---------|
| | | 7 |
-------------------------------------------|
The data from the server are as following:
1 2 4
1 2 5
1 3 6
1 3 7
Every sequence is an array
I need them to be grouped as at the picture above.
Any ideas?
You can use PivotGrid. Example: http://dev.sencha.com/deploy/ext-3.4.0/examples/pivotgrid/simple.html
Unfortunately it is only available in Ext JS 3. It should be available in Ext JS 4.1 though.
It looks like you need to group on the first two columns but unfortunately Ext.data.Store only supports one level of grouping. You'll have to extend Store to support more and Ext.grid.feature.Grouping to take advantage of it.