Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 998
  • Last Modified:

ASP.NET 4 random rows from a query

I'm looking for the easiest way to grab 4 random rows from an SQL query.   I guess I need to know how to extract individual rows from the dataset based on row index or something.
0
drew22
Asked:
drew22
  • 5
  • 4
  • 3
  • +1
1 Solution
 
dfiala13Commented:
How many records are you pulling from?  Might be worth doing in SQL and only returning 4 random rows.
0
 
mkanikCommented:
you can use that code as a reference

<% Option Explicit %>

<!-- #include virtual="/adovbs.inc"--> <%
Dim objConn
Set objConn = Server.CreateObject("ADODB.Connection")
objConn.ConnectionString = "DRIVER=SQL Server;SERVER=OFFICEDNS;" & _
                           "UID=SSDB;PWD=;DATABASE=SSDB;"
objConn.Open
      
Dim objRS
Set objRS = Server.CreateObject("ADODB.Recordset")
objRS.Open "SELECT * FROM tblItem WHERE ParentID IS NULL", objConn, _
           adOpenStatic, adLockReadOnly

Dim rndMax
rndMax = CInt(objRS.RecordCount)
objRS.MoveFirst
      
Do While Not objRS.EOF
      Response.Write objRS("ID") & "<BR>"
      objRS.MoveNext
LOOP
      
objRS.MoveFirst
      
Dim rndNumber
Randomize Timer
rndNumber = Int(RND * rndMax)
      
objRS.Move rndNumber

Response.Write objRS("ID")


objRS.Close
Set objRS = Nothing
      
objConn.Close
Set objConn = Nothing

%>  

0
 
dfiala13Commented:
CREATE TABLE #ROWID(
 DummyID int IDENTITY,
 RealID int)

CREATE TABLE #RandomIDs(
 RealID int)

DECLARE @Total int
DECLARE @i int
DECLARE @iRandomID int
INSERT INTO #ROWID (RealID) SELECT MyID FROM MyTable
SELECT @Total = @@ROWCOUNT


SET @i = 1
WHILE (@i <= 4)
BEGIN
  SET @iRandomID = Convert(int, RAND()*@Total)
  INSERT INTO #RandomIDs(RealID) SELECT FROM #ROWID Where DummyID = @iRandomID

END

SELECT m.* FROM MyTable m Inner Join #RandomIDs r on r.RealID = m.myID
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
drew22Author Commented:
I don't know how to select 4 random rows using SQL on Oracle.
0
 
drew22Author Commented:
sample() doesn't work with multiple tables:
"ORA-30561: SAMPLE option not allowed in statement with multiple table references"


I got a "ORA-00920: invalid relational operator" from this example:
select empno,ename
from ( select * from emp where deptno = 20 order by dbms_random.random)
where rownum <= 3

What about just grabbing 4 random rows from an ASP.NET dataset?
0
 
dfiala13Commented:
Just means you have to move more data across the wire than you need, but still doable.

This assumes rows you want are in table 0 of the dataset...

DataTable dt =  ds.Tables[0];
int iTotal =dt.Rows.Count;
int iRandom = 0;
DataTable dtRandom = dt.Clone();
DataRow dr = null;
for(int i = 0; i < 4; i++){
   iRandom = (new Random().Next(iTotal));
  dr = dt.Rows[iRandom];
  dtRandom.Rows.Add(dr.ItemArray);

}
dg.DataSource = dtRandom;
0
 
drew22Author Commented:
dfiala13,

Is there a possibility that with small datasets you get duplicate random rows?  If the dataset contains 20 rows and you're grabbing 4 randoms,  could you get dupes?
0
 
dfiala13Commented:
Sure,
You could, even in a large dataset.  You can solve this by adding a hashtable and adding an extra step:

DataTable dt =  ds.Tables[0];
int iTotal =dt.Rows.Count;
Hashtable ht = new Hashtable();
int iRandom = 0;
DataTable dtRandom = dt.Clone();
DataRow dr = null;
while(ht.Count < 4){
   iRandom = (new Random().Next(iTotal));
   if(!ht.ContainsValue(iRandom))
     ht.Add(i, iRandom);

}
for(int i = 0; i < ht.Count; i++){
  dr = dt.Rows[(int)ht[i]];
  dtRandom.Rows.Add(dr.ItemArray);
}
dg.DataSource = dtRandom;
0
 
drew22Author Commented:
dfiala,


this part was missing the i var incrementer for ht.Add(), but I added it and it worked.

while(ht.Count < 4){
   iRandom = (new Random().Next(iTotal));
   if(!ht.ContainsValue(iRandom))
     ht.Add(i, iRandom);

}





0
 
dfiala13Commented:
oops.  sorry, should no better than to write code in these boxes.  Glad you got it to work.

If you start needing to pull from more than a few hundred records it would definitely be worth the time to figure out how to make Oracle do the dirty work for you.
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

  • 5
  • 4
  • 3
  • +1
Tackle projects and never again get stuck behind a technical roadblock.
Join Now