Develop Reference

Select row based on dynmically created value

I have a sql table below, value of column parameter and parameter value are dynamically created. The design below is cater for additional parameter being added in later stage. So I think using the parameter and parameter value as column is not ideal for such design.
|---------------------|------------------|------------------|
| Parameter | Parameter Value | Computers |
|---------------------|------------------|------------------|
| Phase | New | PC1 |
|---------------------|------------------|------------------|
| Phase | New | PC2 |
|---------------------|------------------|------------------|
| Phase | Redevelopment | PC3 |
|---------------------|------------------|------------------|
| Cost | High | PC1 |
|---------------------|------------------|------------------|
| Cost | High | PC2 |
|---------------------|------------------|------------------|
| Cost | Cost | PC3 |
|---------------------|------------------|------------------|
Given a scenario where a user search by Phase = "New" AND Cost = "High", it will result in PC1.
At this moment, I could think of is this:
SELECT *
FROM projectParameter
WHERE Parameter = 'Phase' AND Value = 'New' AND Parameter = 'Cost' AND Value = 'High'
Thanks in advance!

First, select all rows that match any part of your filtering.
Then aggregate all those rows to get one result per computer.
Then check each result to see if it contains all the required filtering contraints.
SELECT
Computers
FROM
yourTable
WHERE
(Parameter = 'Phase' AND ParameterValue = 'New')
OR
(Parameter = 'Cost' AND ParameterValue = 'High')
GROUP BY
Computers
HAVING
COUNT(*) = 2

From what I understand, it seems you want list of all computers where there is computer entry for both below conditions :
Parameter = 'Cost' AND Parameter Value = 'High'
Parameter = 'Phase' AND Parameter Value = 'New'
You can try below sql query to see it results your need :
SELECT t.computer
FROM table t
WHERE t.parameter = 'cost'
AND t.parameter_value = 'high'
AND EXISTS (
SELECT computer FROM table where computer=t.computer AND parameter = 'phase' AND parameter_value = 'new');

C# DataSet Designer - AccesDB - Combine two rows into one

I need your help with an SQL query, that I am trying to build in C# Dataset Query Builder...
SELECT HouseHold.HHID, Client.FIRST_NAME, Client.LAST_NAME
FROM ((Client
INNER JOIN HouseHold_Client ON Client.CID = HouseHold_Client.CID)
INNER JOIN HouseHold ON HouseHold_Client.HHID = HouseHold.HHID)
Above code gives me the list of all HouseHolds (their ID) with Clients belonging to them:
HHID | FIRST_NAME | LAST_NAME
------------------------------
1 | Penelope | Grant
1 | Brian | Dyer
2 | James | Newman
2 | Richard | Parsons
.. but I can't figure out how to get people belonging to same HouseHold to show up on the same line, like this for a Data Grid View later on:
HHID | I_FIRST_NAME | I_LAST_NAME | II_FIRST_NAME | II_LAST_NAME
-----------------------------------------------------------------
1 | Penelope | Grant | Brian | Dyer
2 | James | Newman | Richard | Parsons
I have found loads of very similar questions, but very few had the same exact problem to solve. The ones (one or two) that really had the same problem and it had a solution, I just couldn't twist around my problem.
Any help is very much appreciated...
Thank you very much,
AD

Since you have only 2 persons per household, you can use the trick to get the minimum and maximum client Id per household. This is done in a subquery.
SELECT
X.HHID,
C1.FIRST_NAME AS I_FIRST_NAME, C1.LAST_NAME AS I_LAST_NAME,
C2.FIRST_NAME AS II_FIRST_NAME, C2.LAST_NAME AS II_LAST_NAME
FROM
(( SELECT
HHID, Min(CID) AS MinCId, IIf(Max(CID)=Min(CID), Null, Max(CID)) AS MaxCId
FROM HouseHold_Client
GROUP BY HHID
) X
INNER JOIN Client AS C1
ON X.MinCId = C1.CID)
LEFT JOIN Client AS C2
ON X.MaxCId = C2.CID;
The purpose of the IIf() expression is to output the maximum client Id only if it is different from the minimum client Id. To also return a record when MaxCId is Null, a LEFT JOIN is required on C2.
I did not join the HouseHold table here, since we only need the HHID from it, which is also available in HouseHold_Client. You can of course join it as well, if you need other columns from it.
Subquery:
( SELECT
HHID, Min(CID) AS MinCId, IIf(Max(CID)=Min(CID), Null, Max(CID)) AS MaxCId
FROM HouseHold_Client
GROUP BY HHID
) X
Subqueries must be enclosed in parentheses and be given a name (here X). X acts as a normal table having the columns HHID, MinCId and MaxCId in the main query. It is grouped by HHID. I.e., it returns one row per HHID. Min(CID) returns the smallest CID and Max(CID) largest CID per HHID.
In the case where you have 2 clients per HHID, this means that Min and Max will yield these 2 clients. If you have only 1 client, then both Min and Max will return the same client. If this is the case, then the IIf will return Null instead of Max(CID) to avoid returning twice the same client.

Combining Characters with Id Field

I'll create an Issue table in an MVC5 application and I want to use special code for each type of the issues as below:
For IT related questions INF-0001, INF-0002, ...
For General type of questions GEN-0001, GEN-0002, ...
As I use all the issues on the same table, I think it is better to store the ID numbers as INF-0001, GEN-0001, ... etc. In that case should I use string as the data type of ID column in MSSQL? Or what is the best approach in order to store Id's with their related codes? I also think of using GUID, but I am not sure if it is possible. Thanks in advance.

I suppose it's better create separate field for your custom names. So your table will have int Id (Primary Key) field and CustomName varchar(100) or nvarchar(100) type (If you use unicode characters) field with your custom names.
It will be better for perfomance to use int as Id if you will JOIN your file table with others. If you want to search values in this field and it is slow just create INDEX.

You could have a general issue id and a category, for example:
Table: Issue
------------------------------------
IssueID | CategoryID | CategoryIndex
------------------------------------
1 | 1 | 1
2 | 1 | 2
3 | 2 | 1
4 | 1 | 3
Table: Category
-----------------------------
CategoryID | Prefix | Name
-----------------------------
1 | INF | IT
2 | GEN | General
Then you calculate the issue number when querying these tables.
You can store the calculated number in a table if you want to keep track of the issue number in case of a change in the database (ex: the prefix for IT related questions changes from INF to IT)
Now that you have a good schema, how do you keep control of the category sequence on the issues table? Check this out:
DECLARE #categoryID INT
DECLARE #nextSequence INT
SET #categoryID = 1 --You'll have to change this!
SELECT #nextSequence = i.CategoryIndex
FROM Issue i
WHERE i.CategoryID = #categoryID
SELECT COALESCE(#nextSequence, 0) + 1 as 'NextSequence'
You can turn that into a stored procedure (NextSequence, maybe?) that receives an INT as parameter (the category ID) and returns another INT as result (the CategoryIndex for the new issue).
Finally, to create your full code:
SELECT
i.IssueID
, c.Prefix + '-' + RIGHT('0000' + CONVERT(VARCHAR(4), i.CategoryIndex), 4) as 'IssueCode'
FROM Issue i
INNER JOIN Category c ON i.CategoryID = c.CategoryID

Linq to SQL / filter duplicates

i have a view in my sql server 2012 with a couple of duplicates and i want to sort them by the newest and filter all others - can anyone help me?
My viewin my SQL Server 2012:
GUID (as primary key), number, datetime and name
+-----+----------+--------------------------------+-----
| guid | number| datetime | name
+-----+----------+--------------------------------+------
| b105..| 1234567|2014-07-07T16:32:20.854+02:00:00|Name1
| s1b5..| 1111222|2014-07-06T16:30:21.854+02:00:00|Name2
| b17a..| 1234567|2014-07-06T15:22:17.854+02:00:00|Name1
| f205..| 1233333|2014-07-07T17:40:20.854+02:00:00|Name3
| b11t..| 1233333|2014-07-04T11:12:15.854+02:00:00|Name3
| rt85..| 1111222|2014-07-07T21:55:52.854+02:00:00|Name2
+-------+--------+--------------------------------+-----
the name is every time the same if the number is the same. for e.g. number 1234567 is always name 1.
I want to filter my table that i have only the newest number without duplicates
so the result should be:
+-----+----------+--------------------------------+-----
| guid | number| datetime | name
+-----+----------+--------------------------------+------
| b105..| 1234567|2014-07-07T16:32:20.854+02:00:00|Name1
| f205..| 1233333|2014-07-07T17:40:20.854+02:00:00|Name3
| rt85..| 1111222|2014-07-07T21:55:52.854+02:00:00|Name2
+-------+--------+--------------------------------+-----
How can i do this in Linq? "Distinct" is not working because of the guid and the datetime

You can do it by grouping your elements by 2 columns. (number and name). Then access the grouped data. You can do it somehow like that:
var query =
from col in viewData
group col by new
{
col.name,
col.number,
} into groupedCol
select new viewData()
{
number = groupedCol.Key.number,
name = groupedCol.Key.name,
datetime = groupedCol.OrderBy( dateCol => dateCol.datetime).First()
};

var res = list.GroupBy(c => c.name).Select(group => group.OrderBy( c1 => c1.datetime).First()).ToList();
This should work as long as datetime is stored as an instance of DateTime, instead of string.

Union on muliple tables in C#

I am using C# and trying to do union on multiple datatables in the code.
Table 1
ID | Value | Value2
-----------------
1 | Tom | Null
-----------------
2 | John | Null
-----------------
...
Table 2
ID | Value | Value2
-----------------
1 | Null | Susie
-----------------
2 | Null | Kim
-----------------
...
And, I want the result table would be something like
TableResult
ID | Value | Value2
-----------------
1 | Tom | Susie
-----------------
2 | John | Kim
-----------------
...
Is there a way I could this?

I'm not sure what datastructure you are using in C#, but you can do this right in your database:
SELECT COALESCE(Table1.ID, Table2.ID) AS ID
,COALESCE(Table1.Value, Table2.Value) AS Value
,COALESCE(Table1.Value2, Table2.Value2) AS Value2
FROM Table1
FULL OUTER JOIN Table2
ON Table1.ID = Table2.ID
I chose a FULL OUTER JOIN here so that items could be missing on EITHER side (I generally expect most people will use a FULL OUTER JOIN about once a year in their careers), as well as an arbitrary choice to always pick the value in Table1 if it existed first, so Table2 would not overwrite something in Table1.
So as an example of how the FOJ works:
Table 1
1,A,NULL
2,B,X
3,NULL,Y
4,D,Z
Table 2
1,NULL,P
2,NULL,Q
3,C,NULL
5,E,W
Output:
1,A,P
2,B,X
3,C,Y
4,D,Z
5,E,W

If they're already in DataTables, you could load them into another table:
DataTable unionTable = new DataTable();
unionTable.Load(table1.CreateDataReader());
unionTable.Load(table2.CreateDataReader());
I think the notion of doing it server side as previously mentioned is a lot better approach though...

Another way to do this in Linq
//Lets say you have two tables (fill the variables from dababase)
IQueryable tab1 = new List().AsQueryable();
IQueryable tab2 = new List().AsQueryable();
//You can create Result table this way
var resultTable = tab1.Select(t1 => new Table1 { t1.ID, t1.Value, tab2.Any(t2 => t2.ID == t1.ID) ? tab2.First(t2 => t2.ID == t1.ID).Value : null });