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Using a SQL table to handle state transitions

I am working on a Order (MVC) system where the orders transition to different states, i.e new order, paid, shipped, etc. Each state can have multiple transitions. Originally I thought I would have a status table with an ID and Description and then a transition table that would have current status and transitions status, with each transition on a single row. In order to populate a selection box, I would have to do the join to get the descriptions. Now I am thinking I could do it all in one table and add a comma separate column which would list the possible transitions. Is this a good idea or is there a better way?

Any RDBMS promotes database normalization, There are 6 forms of database normalization. Normally if you can get to first three it is good enough.
The first Normal Form states: you should have only one piece of information in a column and a column should store on one piece/Type of information.
Now if your case when you are try to save a comma deliminited list of transitions. if you have to pick only record with a particular type of transitions state?? it will be a messy query.
Also imagine a scenario where you have to update a column for a particular record when transition state is changed, again a very messy , error prone and performance killer query.
Therefore follow the basic rules of Database Normalization, and stick to your 1st which was to create a separate table and use IDs to define transition state, and add a new row whenever a transition changes.
My Suggestion
Simply Have one column for [current status] and one Column for [transition], add a new row everytime any of the values change.
Also a datetime column with default value to current datetime. Which will allow you to go back in history and see different status and transition states of a record in point in time.
Have only one column in only One table which stores this information reference this column in other tables if you need to.

Get Identity Attribute value before inserting in Database

I have a table and it has one of the attribute set as identity. I want to get the value of the identity attribute that would be generated after I enter a value to the database.
I have EmpTable made of EmpID and EmpName. EmpID is set as Identity. I want to fetch the EmpID value before inserting a new row to the database.

I would advise against trying to do this with a table that is set up to use an integer column as the primary key. You will run into concurrency problems if you simply fetch the previous ID and increment it. Instead you should use a GUID (uniqueidentifier in SQL) as your primary key.
This will allow you to generate a new GUID in your code that can safely be saved to the database at a later stage.
http://msdn.microsoft.com/en-us/library/system.guid.newguid.aspx
http://msdn.microsoft.com/en-us/library/ms187942.aspx

Sure the server knows where the auto-increment count is in its sequence, but there is almost nothing useful you can do with that information. Imagine you go to the Post Office and they hand out numbered tickets so they can serve customers in order. Of course you could ask them what the next number they'll give out is, but since anyone can walk in at any time you don't know you'll get that number. If you don't know that you'll get it, you can't do anything with it - e.g. writing it as a reference number on a form would be a mistake.
Depending on what you're trying to do, your two main options are:
Use a client-generated guid as your identifier. This kind of messes up the order so the analogy isn't great, but imagine if each customer who walked in could generate a random number that they are sure would never have been used before. They could use that to fill out forms before taking a number.
Take a number, but do it in a transaction with the other operations. A customer can take a number and use it to fill out some paperwork. If they realize they left their money at home, they just throw everything away and you never call their number.
Why do you think you need this information? Can you use either of these strategies instead?

How to deal with deprecated values in (country-)code lists

Let's say we have a code list of all the countries including their country codes. The country code is primary key of the Countries table and it is used as a foreign key in many places in the database. In my application the countries are usually displayed as dropdowns on multiple forms.
Some of the countries, that used to exists in the past, don't exist any more, for example Serbia and Montenegro, which had the country code of SCG.
I have two objectives:
don't allow the user to use these old values (so these values should not be visible in dropdowns when inserting data)
the user should still be able to (readonly) open old stuff and in this case the deprecated values should be visible in dropdowns.
I see two options:
Rename deprecated values, for instance from 'CountryName' to '!!!!!CountryName'. This approach is the easiest to implement, but with obvious drawbacks.
Add IsActive column to Countries table and set it to false for all deprecated values and true for all other. On all the forms where the user can insert data, display only values which are active. On the readonly forms we can display all values (including deprecated ones) so the user will be able to display old data. But on some of my forms the user should be able to also edit data, which means that the deprecated values should be hidden from him. That means, that each dropbox should have some initialization logic like this: if the data displayed is readonly, then include deprecated values in dropbox and if the data is for edit also, then exclude them. But this is a lot of work and error prone too.
And other ideas?

I deal with this scenario a lot, and use the 'Active' flag to solve the problem, much as you described. When I populate a drop-down list with values, I only load 'active' data and include upto 1 deprecated value, but only if it is being used. (i.e. if I am looking at a person record, and that person has a deprecated country, then that country would be included in the Drop-downlist along with the active countries. I do this in read-only AND in edit modes, because in my cases, if a person record (for example) has a deprecated country listed, they can continue to use it, but once they change it to a non-deprecated country, and then save it, they can never switch back (your use case may vary).
So the key differences is, even in read-only mode I don't add all the deprecated countries to the DDL, just the deprecated country that applies to the record I am looking at, and even then, it is only if that record was already in use.
Here is an example of the logic I use when loading the drop down list:
protected void LoadSourceDropdownList(bool AddingNewRecord, int ExistingCode)
{
using (Entities db = new Entities())
{
if (AddingNewRecord) // when we are adding a new record, only show 'active' items in the drop-downlist.
ddlSource.DataSource = (from q in db.zLeadSources where (q.Active == true) select q);
else // for existing records, show all active items AND the current value.
ddlSource.DataSource = (from q in db.zLeadSources where ((q.Active == true) || (q.Code == ExistingCode)) select q);
ddlSource.DataValueField = "Code";
ddlSource.DataTextField = "Description";
ddlSource.DataBind();
ddlSource.Items.Insert(0, "--Select--");
ddlSource.Items[0].Value = "0";
}
}

If you are displaying the record as read-only, why bother loading the standing data at all?
Here's what I would do:
the record will contain the country code in any case, I would also propose returning the country description (which admittedly makes things less efficient), but when the user loads "old stuff", the business service recognises that this record will be read only, and you don't bother loading the country list (which would make things more efficient).
in my presentation service I will then generally do a check to see whether the list of countries is null. If not (r/w) load the data into the list box, if so (r/o) populate the list box from the data in the record - a single entry in the list equals read-only.

You can filter with CollectionViewSource or you could just create a Public Enumerable that filters the full list using LINQ.
CollectionViewSource Class
LINQ The FieldDef.DispSearch is the active condition. IEnumerable is a little better performance than List.
public IEnumerable<FieldDefApplied> FieldDefsAppliedSearch
{
get
{
return fieldDefsApplied.Where(df => df.FieldDef.DispSearch).OrderBy(df => df.FieldDef.DispName);
}
}

Why would you still want to display (for instance) customer-addresses with their OLD country-code?
If I understand correctly, you currently still have 'address'-records that still point to 'Serbia and Montenegro'. I think if you solve that problem, your current question would be none-existent.
The term "country" is perhaps a little misleading: not all the "countries" in ISO 3166 are actually independent. Rather, many of them are geographically separate territories that are legally portions or dependencies of other countries.
Also note that 'withdrawn country-codes' are reserved for 5 years, meaning that after 5 years they may be reused. So moving away from using the country-code itself as primary key would make sense to me, especially if for historical reasons you would need to back-track previous country-codes.
So why not make the 'withdrawn' field/table that points to the new country-id's. You can still check (in sql for instance, since you were already using a table) if this field is empty or not to get a true/false check if you need it.
The way I see it: "Country" codes may change, country's may merge and country's may divide.
If country's change or merge, you can update your address-records with a simple query.
If country's divide, you need a way to determine what address is part of what country.
You could use some automated system do do this (and write lengthly books about it).
OR
(when it is a forum like site), you could ask the users that still have a withdrawn country that points to multiple alternatives in their account to update their country-entry at login, where they can only choose from the list of new country's that are specified in the withdrawn field.
Think of this simplified country-table setup:
id cc cn withdrawn
1 DE Germany
2 CS Serbia and Montenegro 6,7
3 RH Southern Rhodesia 5
4 NL The Netherlands
5 ZW Zimbabwe
6 RS Serbia
7 ME Montenegro
In this example, address-records with country-id 3, get updated with a query to country-id 5, no user interaction (or other solution) needed.
But address-records that specify country-id 2 will be asked to select country-id 6 or 7 (of course in the text presented to the user you use the country-name) or are selected to perform your custom automated update routine on.
Also note: 'withdrawn' is a repeating group and as such you could/should make it into a separate table.
Implementing this idea (without downtime) in your scenario:
sql statement to build a new country-table with numerical id's as primary key.
sql statement to update address-records with new field 'country-id' and fill this field with the country-id from the new country-table that corresponds with country-code specified in that record's address-field.
(sql statement to) create the withdrawn table and populate the correct data with in it.
then rewrite your the sql statements that supply your forms with data
add the check and 'ask user to update country'-routine
let new forms go live
wait/see for unintended bugs
delete old country-table and (now unused) country-code column from the "address"-table
I am very curious what other experts think about this idea!!

Can i manage employee related data in one table?

I have seen people using ‘DataListValue’ table for storing those values (Call_Types, DepartmentCodes, Divisions and etc) which are used quite often in the drop down list on UI.
This way i can manage them in one table and will have one screen to update codes.
I am wondering if it is okay to keep DepartmentCode,RoleCode,CountryCode in the Data_List Table? Or I should have them in separate table?

It is common practice to have a single codes table that stores code/description pairs with some kind of table type column. For instance, you might commonly see a table like this:
CodesTable
TableId
Code
Description
However, I have never thought it was a good idea. Even if all you store is a code and a description, it's better to make a new table for each set of codes. That way your foreign key relationships will be more clear. Plus, inevitably, you will one day need to store some additional data about one of those code sets and you'll end up needing to add an additional column that only applies to one of the code sets that are stored in the table and the column will be null for all the other rows. It always turns ugly fast.
For instance, lets say, as in the example above, you set TableId to "C" for all the Country codes and you set it to "D" for all Department codes. But then next month a new requirement comes in that requires you to store a postal abbreviation for each Country code. Do you add a PostalAbbreviation column to the table even though it will never apply to Department codes? Or do you create another table that just stores additional data for each country code? How do you know what "C" and "D" mean unless you have some other place to look them up? All around it's just a bad idea.

Using identity fields in a switch statement

I have a SQL lookup table like this:
CREATE TABLE Product(Id INT IDENTITY PRIMARY KEY, Name VARCHAR(255))
I've databound a ASP.NET DropDownList to a LLBLGen entity. User selects a product, and the Id get saved. Now I need to display some product specific details later on. Should I use the Product's ID, and hope the ID is always the same between installations ?
switch (selectedProduct.Id)
{
case 1: //product one
break;
case 2:
case 3: //product two or three
break;
}
or use the name, and hope that never changes?
switch (selectedProduct.Name)
{
case "product one":
break;
}
Or is there a better alternative?

If you know of all the items in this table (which I guess you do if you can do a switch on them) and want them the same for each installation then maybe it should not be an identity column and you should insert 1, 2, 3 with the products themselves.

For this situation, there are three common solutions I have seen:
Hard code the ID - this is quick and dirty, not self-documenting (you don't know what product is being referred to), and prone to breakage as you pointed out. I never use this method anymore.
Enums - I use this when the table is small and static. So, ProductType would be a possible candidate for this. This is self-documenting code, but still creates an awkward connection between code and data where if records are inserted with different IDs than you planned for, then things break. You can mitigate this by automating the Enum generation in various ways, but it still feels wrong. E.g., if your unit tests are inserting records into the Product table, it will be difficult for them to recreate the Enum at that point. Also, if you have 100,000 records, the Enum approach starts to look pretty dumb.
Add an additional column, that is a non-changing identifier. I often use AlphaCode as my column name. So in your case it would look like:
switch (selectedProduct.AlphaCode)
{
case "PRODUCT_ONE":
break;
}
This lets you use an AlphaCode that is self-documenting, allows you to reinsert data without caring about the autoincrement PK value, and lets you change the product name without affecting anything. If you use the AlphaCode approach, ensure that you put a unique index on this column.
The other solution, which is often the most preferable one, is to move this logic to the database. E.g., if product 1 is the product you always want to show by default when its category is selected, you could add a column to your table called IsHeroProduct. Then your query becomes:
if (selectedProduct.IsHeroProduct)
{
//do stuff
}

If you want your ProductID's to be fixed (which doesn't seem to be a good idea), then you can use IDENTITY INSERT (in SQL Server, at least) to ensure ProductID values are the same between installations. But, I would normally only do this for static reference data.
You can also use Visual Studio's T4 templates to generate enums directly off the database data

Some ORMs (LLBLGen at least) can handle this for you; but generating a strong type of enums. I've never used that though.
In these cases, I always just go with an enum that I write myself, but I make sure that all the fields are equal, and update if any change. It becomes more interesting when you work across databases (as I do), but if you take care, it is simple enough.