Develop Reference

How to get Column values?

|No |Type |Num |
| 1 | a | 1 |
| 1 | a | 2 |
| 2 | b | 1 |
| 2 | b | 1 |
| 3 | b | 2 |
| 3 | b | 2 |
I have a Table with columns(No and Type) and I want to create columns(Num) with values. How can I do that in C#?

If you want to split each type into two groups based on no, then you can use window functions:
select t.*,
(case when row_number() over (partition by type order by no) <= 0.5 * count(*) over (partition by type)
then 1 else 2
end) as num
from t;

I'd suggest using dense_rank:
declare #tbl table ([No] int, [Type] varchar(1),[Num] int);
insert into #tbl values
( 1 , 'a' , 1 ),
( 1 , 'a' , 2 ),
( 2 , 'b' , 1 ),
( 2 , 'b' , 1 ),
( 3 , 'b' , 2 ),
( 3 , 'b' , 2 );
select [No], [Type],
dense_rank() over (partition by [Type] order by [Num])
from #tbl

create a method like below and call it
public ExecuteCommand(string columnName,List<string> values)
{
//here 'command' is instance variable of IDbCommand class, to execute command text in database
string sql = "alter table TableName add ColumnName DatatypeOfColumn ";
command.CommandText = sql;
command.ExecuteScalar();
foreach(string value in values)
{
sql = "update table TableName set ColumnName="+ value + " where condition ";
command.CommandText = sql;
command.ExecuteScalar();
}
}

Split query results into unique sets

I have a query which is returning two columns which represents the relationship between two entities (direct or indirect), for example the relationships show in the graph to the right would be represented by the data in the table to the right:
| From | To | 1 3 4
|------|----| o----o----o
| 1 | 3 | / \
| 1 | 4 | / \
| 1 | 5 | 2 o o 5
| 2 | 3 |
| 2 | 4 |
| 2 | 5 |
| 3 | 4 | 6 7
| 3 | 5 | o----o
| 6 | 7 |
What I want to do is group this data into a number of sets, equal to the number of distinct graphs described by the relationships (so 2 sets in the above example).
This grouping could happen as part of the database query (T-SQL) or once the data is in memory (C#).

It may not be pretty, but this will group the vertexes properly and only requires edges as a starting point. Note that the order of the vertexes for an edge does not matter.
-- Sample data.
declare #Edges as Table ( Vertex1 Int, Vertex2 Int );
insert into #Edges ( Vertex1, Vertex2 ) values
( 1, 3 ), ( 3, 4 ), ( 3, 2 ), ( 3, 5 ),
( 6, 7 );
select * from #Edges;
-- Create a working table that assigns each vertex to a unique "set".
declare #Sets as Table ( SetId Int, Vertex Int );
insert into #Sets ( SetId, Vertex )
select Row_Number() over ( order by Vertex ), Vertex from (
select distinct Vertex1 as Vertex from #Edges
union
select distinct Vertex2 from #Edges ) as PH;
select * from #Sets;
-- Update the working table to group vertexes into sets:
-- For each vertex update the SetId to the minimum SetId of all of the vertexes one edge away.
-- Repeat until nothing changes.
declare #UpdatedRows as Int = 42;
while #UpdatedRows > 0
begin
update NS
set SetId = MinSetId
from (
select S.SetId, S.Vertex,
( select Min( SetId ) from #Sets where Vertex in (
select S.Vertex union
select Vertex1 from #Edges where Vertex2 = S.Vertex union
select Vertex2 from #Edges where Vertex1 = S.Vertex )
) as MinSetId
from #Sets as S ) as NS
where SetId != MinSetId;
set #UpdatedRows = ##RowCount;
select * from #Sets; -- Show the work as it progresses.
end
-- The SetId values can be collapsed using Dense_Rank .
select Dense_Rank() over ( order by SetId ) as SetId, Vertex
from #Sets;

Optimal way to analyze user qualifications data (C# and SQL server)

I need to analyze data from SQL server table. Table contains data connected with qualifications of all employyes in the company and has the following structure (simplified):
| User | Qualification | DateOfQualificationAssignment |
| user000 | Junior | 2014-01-15 |
| user000 | Middle | 2014-02-15 |
| user001 | Middle | 2014-02-02 |
| user001 | Senior | 2014-03-18 |
| user002 | Senior | 2014-02-19 |
| user003 | Junior | 2014-03-04 |
I need the way to determine number of employees having given qualification for the concrete date. It should be some sort of analyze("Qualification", "Date") function returning the folowing for these types of input data:
analyze("Junior", '2014-01-20') - returns 1 (it is user user000)
analyze("Junior", '2014-02-20') - returns 0 (because user000 became Middle on 2014-02-15)
analyze("Middle", '2014-02-25') - returns 2 (because user000 and user001 are having Middle qualification on 2014-02-25)
analyze("Middle", '2014-03-28') - returns 1 (user000 is still Middle, but user001 became Senior on 2014-03-18)
Currently I have no idea how to handle this efficiently. What approach can be used to achieve my goal?

Think this should satisfy your requirements:
create function dbo.analyze(#qualification varchar(50), #date date)
returns int
as
begin
declare #result int;
with cte
as
(
select t.*, rank() over (partition by t.[User] order by t.DateOfQualificationAssignment desc) r
from theTable t -- no clue what the real table is named
where t.DateOfQualificationAssignment < #date
)
select #result = count(*)
from cte
where cte.r = 1 and cte.Qualification = #qualification
return #result;
end
go
Tested with your data:
create table theTable
(
[User] varchar(50) not null,
Qualification varchar(50) not null,
DateOfQualificationAssignment date not null
)
go
insert into theTable([User],Qualification,DateOfQualificationAssignment)
values
('user000','Junior','20140115'),
('user000','Middle','20140215'),
('user001','Middle','20140202'),
('user001','Senior','20140318'),
('user002','Senior','20140219'),
('user003','Junior','20140304')
go
and the results:
select dbo.analyze('Junior','20140120') --returns 1
go
select dbo.analyze('Junior','20140220') --returns 0
go
select dbo.analyze('Middle','20140225') --returns 2
go
select dbo.analyze('Middle','20140328') --returns 1
go

Use row_number() over() in a derived table to enumerate the rows on DateOfQualificationAssignment descending partitioned by User where DateOfQualificationAssignment is less than the date you want to check on.
In the main query you count the rows with the enumerated value 1 and Qualification.
SQL Fiddle
MS SQL Server 2012 Schema Setup:
create table T
(
[User] char(7),
Qualification char(6),
DateOfQualificationAssignment date
)
insert into T values
('user000', 'Junior', '2014-01-15'),
('user000', 'Middle', '2014-02-15'),
('user001', 'Middle', '2014-02-02'),
('user001', 'Senior', '2014-03-18'),
('user002', 'Senior', '2014-02-19'),
('user003', 'Junior', '2014-03-04')
Query 1:
declare #Qualification char(6) = 'Middle'
declare #Date date = '2014-03-28'
select count(*)
from (
select T.Qualification,
row_number() over(partition by T.[User] order by T.DateOfQualificationAssignment desc) as rn
from T
where T.DateOfQualificationAssignment < #Date
) as T
where T.rn = 1 and
T.Qualification = #Qualification
Results:
| COLUMN_0 |
|----------|
| 1 |

Using "PIVOT" in SQL

I made this question a while back.
SQL Server making rows into columns
Basically, the person that answered explained very well what I needed to do. However, I encountered a problem
aID| status | group |
-----------------------
1 | acti | group1 |
2 | inac | group2 |
A3 | acti | group1 |
Second Table: This table is fixed. It has around 20 values and the IDs are all numbers
atID| traitname |
------------------
1 | trait1 |
2 | trait2 |
3 | trait3 |
Third Table: This table is used to identify the traits the assets in the first table have. The fields that have the same name as fields in the above tables are obviously linked.
tID| aID | atID | trait |
----------------------------------
1 | 1 | 1 | NAME |
2 | 1 | 2 | INFO |
3 | 2 | 3 | GOES |
4 | 2 | 1 | HERE |
Now, the user wants the program to output the data in the following format:
aID| status | group | trait1 | trait2 | trait 3
-------------------------------------------------
1 | acti | group1 | NAME | INFO | NULL
2 | inac | group2 | HERE | NULL | GOES
A3 | acti | group1 | NULL | NULL | NULL
Now, the problem here is that, as you can see, A3 has no trait. In the final view, I would want A3 to appear completely null in the traits. But it doesn't appear at all, even though it's there. Does anyone know how can I fix this?
Here is the query I am using:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME(traitname)
from Table2
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT aid, status, [group],' + #cols + '
from
(
select t1.aid,
t1.status,
t1.[group],
t2.traitname,
t3.trait
from table1 t1
inner join table3 t3
on t1.aid = t3.aid
inner join table2 t2
on t3.atid = t2.atid
) x
pivot
(
max(trait)
for traitname in (' + #cols + ')
) p '
execute sp_executesql #query;

The problem is you are using an INNER JOIN on your tables. An INNER JOIN returns all rows that have matching data in both tables.
Since you want to return everything from Table1, you will alter your query to use a LEFT JOIN instead of the INNER JOIN:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME(traitname)
from Table2
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT aid, status, [group],' + #cols + '
from
(
select t1.aid,
t1.status,
t1.[group],
t2.traitname,
t3.trait
from table1 t1
left join table3 t3
on t1.aid = t3.aid
left join table2 t2
on t3.atid = t2.atid
) x
pivot
(
max(trait)
for traitname in (' + #cols + ')
) p '
execute sp_executesql #query;
As a side note, it is difficult to tell what the data types on your join columns are. Your Table1.aid column appears to be a varchar because of the A3 value but your Table3.aid column looks to be an int. If your data types are not the same, then you will need to cast the data on the join similar to -- on t1.aid = cast(t3.aid as varchar(10))

I need help constructing a SQL query to return counts of a column for Jan-Dec based on my Date Column

I'm not an expert at SQL and i'm not even sure if this type of query is doable.
I want to return a count(*) for each "MediaTypeID" for each Month based off of "MediaDate".
Any help would be greatly appreciated!
Thanks.
My Table looks like:
The Table Data looks like:
1 | 1 | Funny Cat Video | 2006-01-25 00:00:00.000
2 | 1 | Funny Dog Video | 2006-01-20 00:00:00.000
3 | 2 | Angry Birds Game | 2006-03-13 00:00:00.000
4 | 4 | Blonde Joke | 2006-03-16 00:00:00.000
5 | 3 | Goofy Clown Picture | 2006-02-27 00:00:00.000
6 | 2 | Racing Game | 2006-02-10 00:00:00.000
7 | 1 | Star Wars Video | 2006-07-15 00:00:00.000
The query would return 12 rows of results for Jan-Dec looking like:
Month | MediaTypeID1Count | MediaTypeID2Count | MediaTypeID3Count | MediaTypeID4Count
Jan | 400 | 255 | 15 | 65
Feb | 100 | 25 | 75 | 35
Mar | 320 | 155 | 50 | 99
Apr | 56 | 0 | 98 | 313

This type of data transformation is known as a PIVOT. SQL Server 2005+ has a pivot function that can be implemented:
select month,
[1] MediaType1_count,
[2] MediaType2_count,
[3] MediaType3_count,
[4] MediaType4_count
from
(
select
mediatypeid,
datename(m, mediadate) Month,
datepart(m, mediadate) monnum
from yourtable
) src
pivot
(
count(mediatypeid)
for mediatypeid in ([1], [2], [3], [4])
) piv
order by monnum
See SQL Fiddle with Demo
If you have an unknown number of values that you want to transpose into columns, then you can use dynamic sql:
DECLARE #cols AS NVARCHAR(MAX),
#colNames AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME(mediatypeid)
from yourtable
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
select #colNames = STUFF((SELECT distinct ', ' + QUOTENAME(mediatypeid) +' as MediaType' + cast(mediatypeid as varchar(50))+'_Count'
from yourtable
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT month,' + #colNames + ' from
(
select mediatypeid,
datename(m, mediadate) Month,
datepart(m, mediadate) monnum
from yourtable
) x
pivot
(
count(mediatypeid)
for mediatypeid in (' + #cols + ')
) p
order by monnum'
execute(#query)
See SQL Fiddle with Demo
The result will look like:
| MONTH | MEDIATYPE1_COUNT | MEDIATYPE2_COUNT | MEDIATYPE3_COUNT | MEDIATYPE4_COUNT |
----------------------------------------------------------------------------------------
| January | 2 | 0 | 0 | 0 |
| February | 0 | 1 | 1 | 0 |
| March | 0 | 1 | 0 | 1 |
| July | 1 | 0 | 0 | 0 |

I think this may be what you are looking for. The following will simply return the count based off the media type id, then group by year and then its month
Select MediaTypeID, datepart(year, MediaDate), datepart(month, MediaDate), count(*)
From Media
Group by MediaTypeID, datepart(year, MediaDate), datepart(month, MediaDate)

In my opinion, this could be a good challenge for you to start with this code:
Declare #T Table (
MediaID BigInt Primary Key Identity(1, 1)
, MediaTypeID BigInt
, MediaTitle Nvarchar(50)
, MediaDate DateTime
);
Insert #T (
MediaTypeID
, MediaTitle
, MediaDate
) Select 1
, 'Funny Cat Video'
, '2006-01-25 00:00:00.000'
Union
Select 1
, 'Funny Dog Video'
, '2006-01-20 00:00:00.000'
Union
Select 2
, 'Angry Birds Game'
, '2006-03-13 00:00:00.000'
Union
Select 4
, 'Blonde Joke'
, '2006-03-16 00:00:00.000'
Union
Select 3
, 'Goofy Clown Picture'
, '2006-02-27 00:00:00.000'
Union
Select 2
, 'Racing Game'
, '2006-02-10 00:00:00.000'
Union
Select 1
, 'Star Wars Video'
, '2006-07-15 00:00:00.000'
;
Select Month.Title
, Count(Type01_Result.MediaID) As MediaTypeID_1
, Count(Type02_Result.MediaID) As MediaTypeID_2
, Count(Type03_Result.MediaID) As MediaTypeID_3
, Count(Type04_Result.MediaID) As MediaTypeID_4
From (
Select 1 As Id
, 'Jan' As Title
Union
Select 2
, 'Feb'
Union
Select 3
, 'March'
Union
Select 4
, 'April'
Union
Select 5
, 'May'
Union
Select 6
, 'June'
Union
Select 7
, 'July'
Union
Select 8
, 'Aug'
Union
Select 9
, 'Sept'
Union
Select 10
, 'Nov'
Union
Select 11
, 'Oct'
Union
Select 12
, 'Dec'
) As Month
Left Outer Join
#T As Type01_Result
On Type01_Result.MediaTypeID = 1
And DatePart(Month, Type01_Result.MediaDate) = Month.Id
Left Outer Join
#T As Type02_Result
On Type02_Result.MediaTypeID = 2
And DatePart(Month, Type02_Result.MediaDate) = Month.Id
Left Outer Join
#T As Type03_Result
On Type03_Result.MediaTypeID = 3
And DatePart(Month, Type03_Result.MediaDate) = Month.Id
Left Outer Join
#T As Type04_Result
On Type04_Result.MediaTypeID = 4
And DatePart(Month, Type04_Result.MediaDate) = Month.Id
Group By Month.Title
;
The only thing is that you should be carefull about the year value and how many years you wanna include in the output, because this result will give you the summation of all records in each month no matter which year the date of the record is. It may cause some confusion in the result.
(Remember that I always set the tab size to 8 characters in the Options of Management Studio, so I suggest you do that to see the correct style of writing T-SQL)
Hope it helps you.
Cheers