Database

28-Aug-04 22:55

NewPureLand wrote:
Is there any one who can make it perfect for on my question?

You have to ask a better question. Just posting some code and saying help me is not enough. What is wrong with the code? What error is happening? What is it supposed to do? And, what does it do?

Answer these questions and you might give enough information for someone to help you quickly.

"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell

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Re: SQL question

mike.hall@lehigh.edu30-Aug-04 2:46

mike.hall@lehigh.edu

30-Aug-04 2:46

Take a look at your select statement. classid and nclassid will be evaluated as literals making them part of the string. Your select statement would then look like "select * from brand where class_id=classid..." instead of "select * from brand where class_id=5..." which is what you really want. Be sure to force the evaluation of these variables before executing your query.

functions

jairajanbrothers27-Aug-04 23:42

jairajanbrothers

27-Aug-04 23:42

hhow toexecute the functions

jairaj

Mazdak27-Aug-04 23:51

Mazdak

27-Aug-04 23:51

See EXECUTE in SQL Server Online Book.

Mazy

"One who dives deep gets the pearls,the burning desire for realization brings the goal nearer." - Babuji

Colin Angus Mackay28-Aug-04 2:04

28-Aug-04 2:04

Actually, you don't EXECUTE functions. You do that to Stored Procedures.

Mazdak28-Aug-04 3:10

Mazdak

28-Aug-04 3:10

According to Sql Server online book ,it does that too.

Mazy

"One who dives deep gets the pearls,the burning desire for realization brings the goal nearer." - Babuji

Colin Angus Mackay28-Aug-04 4:31

28-Aug-04 4:31

Are you sure? I've checked the books online and I cannot see anything about running functions with the EXECUTE COMMAND. I also created a sample, on the Northwind database, to try out.

CREATE FUNCTION dbo.AllProducts()
RETURNS TABLE
AS
RETURN(SELECT * FROM PRODUCTS)

Then I tried to execute it like this:

EXECUTE dbo.AllProducts

I got an error message

Server: Msg 2809, Level 18, State 1, Line 1
The request for procedure 'AllProducts' failed because 'AllProducts' is a function object.

Mazdak28-Aug-04 4:40

Mazdak

28-Aug-04 4:40

Its very strange,I have not test it myself before but this is from my Online Book for EXECUTE command:

Executes a scalar-valued, user-defined function, a system procedure, a user-defined stored procedure, or an extended stored procedure

Confused | :confused:

Mazy

"One who dives deep gets the pearls,the burning desire for realization brings the goal nearer." - Babuji

Colin Angus Mackay28-Aug-04 2:04

28-Aug-04 2:04

To run a User Defined Function (or UDF) you need to do something like:

SELECT * FROM dbo.MyFunctionName()

Rocky Moore31-Aug-04 19:55

Rocky Moore

31-Aug-04 19:55

Depends on the type of function, that is, what it returns. If it is a value you can just use:

set @MyValue = MyFunction(MyParameter)

If it returns a table, you would probably use it in a FROM or where you would normally specify a table.

Rocky <><
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Mdb question

jzb27-Aug-04 23:40

jzb

27-Aug-04 23:40

I use ado.net do something to mdb database. I found out the mdb database's size was been increased when it run some time.I can't confirm what it is cause.
It is my class,

using System;
using System.Data;
using System.Data.OleDb;
using System.Collections;

namespace RoadLib
{
///
/// NdnDataBase の概要の説明です。
///
public class NdnDataBase
{
protected string m_strConnectionString;
private OleDbConnection m_connection = null;
private OleDbTransaction m_transaction = null;

///
/// NdnDataBase の概要説明です
///
public NdnDataBase()
{
//
// TODO: コンストラクタロジックをここに追加してください。
//
m_connection = null;
}
///
/// NdnDataBase の概要説明です
///
///
public NdnDataBase(string strConnectionString)
{
m_strConnectionString = strConnectionString;

m_connection = null;
}

///
/// DBコネクションを取得します
///
public OleDbConnection connection
{
get { return m_connection; }
}

///
/// DBトランザクションを取得します
///
public OleDbTransaction transaction
{
get { return m_transaction; }
}

///
/// データベースを開くために使用接続する
///
public string connectionString
{
get { return m_strConnectionString; }

set { m_strConnectionString = value;}
}

///
/// 指定のデータベースでセッションを開く
///
///
public OleDbConnection DBOpen()
{
if(m_connection == null)
{
try
{
//データベース接続パラメータを取得
if (m_strConnectionString == "")
{
return null;
}
m_connection = new OleDbConnection(m_strConnectionString);

//DBオープン
m_connection.Open();
}
catch(Exception err)
{
//NdnPublicFunction.WriteLog(m_strLogFileName, err.Message);
m_connection = null;
throw (err);
}
}

return m_connection;
}

///
/// データベースでセッションを閉じる
///
///
public void DBClose()
{
try
{
//DBクローズ
if (m_connection != null)
{
m_connection.Close();
}
}
catch
{
}
finally
{
//初期値を設定
m_transaction = null;
m_connection = null;
}
}

///
/// SQLステートメントを実行
///
///
///
///
///
public bool ExecSql(string strCommandText, OleDbConnection connection, OleDbTransaction transaction)
{
bool bReturn = false;
OleDbCommand dbCommand = new OleDbCommand(strCommandText, connection, transaction);
try
{
dbCommand.ExecuteNonQuery();
bReturn = true;
}
catch( Exception err)
{
throw (err);
}
return bReturn;
}

///
/// データベースでトランザクションを開始します
///
///
public bool BeginTrans()
{
bool bReturn = false;
try
{
if (m_connection != null)
{
m_transaction = m_connection.BeginTransaction();
bReturn = true;
}
}
catch (Exception err)
{
throw err;
}
return bReturn;
}

///
/// データベースでトランザクションをコミットします
///
///
public bool CommitTrans()
{
bool bReturn = false;
try
{
if (m_transaction != null)
{
m_transaction.Commit();
bReturn = true;
}
}
catch (Exception err)
{
throw err;
}
finally
{
m_transaction = null;
}
return bReturn;
}

///
/// データベースでトランザクションをロールバックします
///
///
public bool RollbackTrans()
{
bool bReturn = false;
try
{
if (m_transaction != null)
{
m_transaction.Rollback();
bReturn = true;
}
}
catch (Exception err)
{
throw err;
}
finally
{
m_transaction = null;
}

return bReturn;
}

}
}

I use it to operate mdb database.
for example:

NdnDataBase database = new NdnDataBase("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=d:\nara.mdb;User Id=adminassword=;");
try
{
database.DBOpen();
database.BeginTrans();
database.ExecSql("Delete from ttt");
...
database.ExecSql("Insert into ttt values(1, 2)", database.connection, database.transaction);

database.CommitTrans();
...
}
catch
{
database.RollbackTrans();
}
finally
{
database.DBClose();
}

it operation is in a timer event.

At last when the mdb database's size be to some size, the database is bad.

Re: Mdb question

Colin Angus Mackay28-Aug-04 2:08

ado.net connections and .dispose?

28-Aug-04 2:08

I'm not reading throught all that code. You have to be more specific.

While scrolling, however, I did notice that you are sending commands to the database that modify the contents of the database. So of course the file is going to expand. Typically databases files only ever expand until you explicitly run some sort fo compression or free space removal command on them.

Roger Alsing27-Aug-04 1:39

Roger Alsing

27-Aug-04 1:39

Im just reading an ms press book about ado.net

here it says

"if teh connection is ".closed" the connection is returned to the pool and ready for reuse..
if the connection is ".disposed" the object is deleted from memory and cannot be reused by the pool"

is this really true?

i thought it was just the .net object wrapping the native connection that was killed and removed when disposing.

isn the actual pooling handled by oledb internally or something?

//Roger

Colin Angus Mackay28-Aug-04 2:12

28-Aug-04 2:12

IIRC the connection pool is internal to your ASP.NET application, not the database engines (some database engines don't support native pooling anyway). So if you dispose of a connection it will be released from the pool. If you just close the connection, it just gets stored in the pool until something wants a connection with the same connection string. This is much quicker than actually going back to the server and requesting a connection from there.

Roger Alsing29-Aug-04 20:25

Roger Alsing

29-Aug-04 20:25

wrong.. found the answer on msdn

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemDataSqlClientSqlConnectionClassDisposeTopic1.asp[^]

"The Dispose method calls Close, and returns the SqlConnection to the connection pool."

//Roger

Colin Angus Mackay30-Aug-04 1:27

30-Aug-04 1:27

Which means that your MS Press book is wrong. I never said I was right, I just said "If I Recalled Correctly"

Rocky Moore31-Aug-04 20:01

Rocky Moore

31-Aug-04 20:01

Sorry, I did not read this earlier.. Just wrote up a tip about it yesterday as someone else asked me the question about a week ago. I did not remember correctly and did some research. Come to the same conclusion as the thread here. Many people have argued that the dispose actually would not allow it to be used in the connection pool. Who is right and wrong? In the use net groups there were people who worked on the code that said absolutely that there was little difference. About the only thing the dispose did that close did not was delete the connection string.

Here is more info along with preventing a leak:

http://www.hintsandtips.com/ShowTip/129/hat.aspx[^]

Rocky <><
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Identity primary key

Diego F.26-Aug-04 23:18

Diego F.

26-Aug-04 23:18

Hi. I have a table with a primary key that I'd like to be an identity, so I don't worry about giving it a value manually (just increases automatically. 1, 2, 3, ...)

The problem is that I have another table where these key is a foreign key, so in my application, I must fill the value manually to the second table, but then I need to get the value in the first table.

I mean, imagine I have a table with: (id, name, age), where 'id' is the primary key and is identity, with values 1,2,...

Then I have another table with: (id, phone), where 'id' is the foreign key.

In my application, I can fill entries in the first table without giving values to id, as it is done automatically, but in the second table, I must give manually the values. How can I do that?

Should I make a query to get the 'id'?

Regards,

Diego F.

David Salter26-Aug-04 23:28

David Salter

26-Aug-04 23:28

You can get an the last inserted identity (on SQL Server) by calling

select @@identity

You can then insert this into your second table.

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Diego F.26-Aug-04 23:50

Diego F.

26-Aug-04 23:50

Thanks. I was searching about this and I found also SCOPE_IDENTITY(). Apart from using one or the other, how can I get the value in my application.

I mean, I saw people using: "Select @value = scope_identity()", but where do I catch the @value variable?

Regards,

Diego F.

David Salter27-Aug-04 1:12

David Salter

27-Aug-04 1:12

If you do a select @@identity, you get the results into your application exactly the sameway that you do with any other select statement.

With select @@identity, you do not need to select the value into a variable.

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Colin Angus Mackay27-Aug-04 1:33