Database Discussion Boards

Re: Need help to select max date

Paul Conrad15-Jul-07 19:17

Paul Conrad

15-Jul-07 19:17

Does that one do what you need it to?

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

Re: Need help to select max date

masyarial15-Jul-07 20:55

masyarial

15-Jul-07 20:55

Yes, you all great !!!

Thanks a lot.

B.regards

Re: Need help to select max date

masyarial15-Jul-07 22:15

masyarial

15-Jul-07 22:15

Hi All, sorry to bothering you again, need your help.
my format date is complete like "7/12/2007 10:40:49 AM"
so, concern that time/date is different each row, example (i write date as integer)

name type value date
-----------------------------------------------
a A 1 1
a B 1 2
a C 1 3
a A 2 4
a B 2 5
a C 2 6

when I run the code the result is:
name date A B C
----------------------------------------
a 6 0 0 2

so, the code show value each name with maximum date,
not show value each name, each type with maximum date.

so, i very confuse, realy need your help, thanks

SQL SERVER

magedhv15-Jul-07 0:27

magedhv

15-Jul-07 0:27

how do i make a backup plan that can backup the database to another location automaticly

Re: SQL SERVER

Paul Conrad15-Jul-07 5:14

Paul Conrad

15-Jul-07 5:14

SQL Server 2000 Backup and Restore[^] might be of help.

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

Re: SQL SERVER

sidbaruah17-Jul-07 19:08

sidbaruah

17-Jul-07 19:08

Use maintenance plans in SQL Management!!!

I was born dumb!!
Laugh | :laugh:

Programming made me laugh Laugh | :laugh:

!!!
--sid--

Import DB diagram in Visiso

merwa14-Jul-07 22:06

merwa

14-Jul-07 22:06

How to Import the SQL DataBase Diagram In visio

merwa

Re: Import DB diagram in Visiso [modified]

martin_hughes15-Jul-07 13:09

martin_hughes

15-Jul-07 13:09

I don't think you can import it directly... but depending on the version of Visio you are using, you can tell it to create a diagram from a database by going to:

Tools > Options > Add-ins > Database Wizard

or Database > Reverse Engineer...

and following the instructions.

"It was the day before today.... I remember it like it was yesterday."

-Moleman

Sql query find the primary key ,foreign key relationship between tables

Rmesh13-Jul-07 23:41

Rmesh

13-Jul-07 23:41

How to write query to find relationship between the primary key and foreign key re lation ship between the tables

Re: Sql query find the primary key ,foreign key relationship between tables

Paul Conrad14-Jul-07 7:16

Paul Conrad

14-Jul-07 7:16

Elaborate a bit more about your question. What database are you using?

"Any sort of work in VB6 is bound to provide several WTF moments." - Christian Graus

Re: Sql query find the primary key ,foreign key relationship between tables

Colin Angus Mackay14-Jul-07 10:28

Colin Angus Mackay

14-Jul-07 10:28

Rmesh wrote:
How to write query to find relationship between the primary key and foreign key re lation ship between the tables

That depends on the database you are using. In SQL Server there are sys* tables and INFORMATION_SCHEMA views that will allow you to get at this information.

Upcoming events:
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Ready to Give up - Your help will be much appreciated.

My website

Re: Sql query find the primary key ,foreign key relationship between tables

Paul Conrad14-Jul-07 10:50

Paul Conrad

14-Jul-07 10:50

Colin Angus Mackay wrote:
depends on the database you are using

That is why I asked earlier. easy in SQL, but I am not sure about Access. I've looked at some of the system table and it might be a little more work.

"Any sort of work in VB6 is bound to provide several WTF moments." - Christian Graus

System.OverflowException for large Decimal value

Uwe Keim13-Jul-07 23:35

Uwe Keim

13-Jul-07 23:35

Having a website that is dealing with large numbers, I am storing values inside a decimal(36,18) SQL Server 2005 column.

Until recently, everything run smooth for about 1 year.

Then it crashed with a System.OverflowException exception ("Conversion overflows.") and the following stack trace (excerpt):

at System.Data.SqlClient.SqlBuffer.get_Decimal()
   at System.Data.SqlClient.SqlBuffer.get_Value()
   at System.Data.SqlClient.SqlDataReader.GetValueInternal(Int32 i)
   at System.Data.SqlClient.SqlDataReader.GetValues(Object[] values)
   at System.Data.ProviderBase.DataReaderContainer.CommonLanguageSubsetDataReader.GetValues(Object[] values)
   at System.Data.ProviderBase.SchemaMapping.LoadDataRow()
   at System.Data.Common.DataAdapter.FillLoadDataRow(SchemaMapping mapping)
   ...

The value it seems to be unable to read from the database is 90807364313.118401000000000000 (i.e. a rather huge, approx. 90 billions Wink | ;-)

).

Now after digging, I found this thread at Google Groups. [^].

This thread, from 2004, tells that this is a bug in the .NET framework and that it will be fixed in next version. Now since it is already the next version, I am rather clueless.

Question: Anyone knows a hint or a workaround/fix for this issue? Maybe a hotfix from Microsoft is available?

Thanks
Uwe

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Re: System.OverflowException for large Decimal value [modified]

Mike Dimmick14-Jul-07 5:51

Mike Dimmick

14-Jul-07 5:51

The .NET Framework documentation states:

"The Decimal data type provides the greatest number of significant digits for a number. It supports up to 29 significant digits and can represent values in excess of 7.9228 x 10^28. It is particularly suitable for calculations, such as financial, that require a large number of digits but cannot tolerate rounding errors."

Your number is larger than 2^96 in the mantissa portion. It simply won't fit in the data type. Your only workaround is to use ToDouble, as in the thread, which will lose some precision (as double is only 64 bits). If you need something larger, you will need to implement your own scaled integer class and access the data as raw binary using GetBytes.

[EDIT:] It looks like you should be able to use the SqlDecimal type. I see you're using GetValues to retrieve all of the row's values in one go. Consider using GetSqlValues instead, to use the SQL types. I've not tried this.

-- modified at 11:57 Saturday 14th July, 2007

Stability. What an interesting concept. -- Chris Maunder

Re: System.OverflowException for large Decimal value

Uwe Keim14-Jul-07 5:55

Uwe Keim

14-Jul-07 5:55

D'oh!

Thank you very much, Mike, I didn't even care to look for the docs of double, since I implied that decimal is the largest numeric type. Stupid me!

Thanks for your hints!

Re: System.OverflowException for large Decimal value

Uwe Keim14-Jul-07 6:47

Uwe Keim

14-Jul-07 6:47

Trying a litte bit more, I wrote this simple test application:

internal sealed class Program
{
  private static void Main()
  {
    double v5 = 90807364313.118401000000000000;
    decimal v6 = 90807364313.118401000000000000m;
  
    Console.WriteLine( v5 ); // Outputs 90807364313.1184
    Console.WriteLine( v6 ); // Outputs 90807364313.11840100000000000
  }
}

Since both data types are able to store the original value, I cannot follow your initial explainations.

I still do think this is a bug in the ADO.NET framework.

Re: System.OverflowException for large Decimal value

Mike Dimmick14-Jul-07 8:30

Mike Dimmick

14-Jul-07 8:30

Both of those are losing significant digits. double uses binary floating point notation - the exponent is expressed internally as a power of two. 11 bits are used for the exponent and 52 for the mantissa (the actual significant digits), the final bit being used for the sign. The largest mantissa that can be represented is 2^52 - 1 which is 4,503,599,627,370,495, effectively 15 significant decimal digits. For more on double, see IEEE-754 on Wikipedia[^] and What Every Computer Scientist Should Know About Floating-Point Arithmetic[^]. Since the position of the decimal point is represented as a binary exponent, only negative powers of two and sums of negative powers of two can be represented. Everything else is rounded. For example, consider 1/3 in decimal (0.3333 recurring) which can never be truly represented.

The decimal value only has 17 digits after the decimal point. It's kept the magnitude correct at the expense of losing the final 0. You can only get 28 whole significant digits with this format - your database definition has 38. SqlDecimal supports the same range that SQL Server does.

Stability. What an interesting concept. -- Chris Maunder

Re: System.OverflowException for large Decimal value

Uwe Keim14-Jul-07 8:36

Uwe Keim

14-Jul-07 8:36

Thanks, Mike, I really do appreciate your feedback.

Even if you (which I have no doubt!) are correct with your explainations, what practical chance do I have to apply them?

Since I'm simply doing kind of "SELECT * FROM ..." and receiving a DataTable, i do see no simply/any way to tell ADO.NET not to do the automatic conversion to decimal.

Any ideas?

Thanks
uwe

Re: System.OverflowException for large Decimal value

Mike Dimmick14-Jul-07 8:54

Mike Dimmick

14-Jul-07 8:54

If you're using .NET 2.0, you may be able to set the ReturnProviderSpecificTypes property to true, to get the DataTable to use SqlDecimal internally. With .NET 1.1 you probably have to drop back down to using a SqlDataReader.

Stability. What an interesting concept. -- Chris Maunder

Re: System.OverflowException for large Decimal value

Uwe Keim14-Jul-07 8:57

Uwe Keim

14-Jul-07 8:57

Yes, that DataAdapter.ReturnProviderSpecificTypes is what I found, too.

I'll try that and post the result here for reference purposes.

Thank you again!

Re: System.OverflowException for large Decimal value

Uwe Keim14-Jul-07 20:15

Uwe Keim

14-Jul-07 20:15

Feedback: When using the ReturnProviderSpecificTypes (setting it to true), I succeeded.

I can do the conversion from the SqlXxx data types (e.g. SqlDecimal) to native CLR data types be myself, and not let it ADO.NET do it automatically.

Thanks for your help!

using datagrid in vb.net

Rharzkie13-Jul-07 23:16

Rharzkie

13-Jul-07 23:16

hi! i just wanna ask if it is possible for a datagrid to view some of the contents of a database, then another contents afterwards???

for example, I click the search button to search a particular school subjects. E.g. i search for subject "Theology", then all students who enroll in "theology" should be display, then i will going to search the subject "college algebra", all the students who enrolled in that will be viewed???

What code i will going to use there? will i use the OleDbDataAdapter??? If not, what should i do for it????

Re: using datagrid in vb.net

Manas Bhardwaj14-Jul-07 4:49

Manas Bhardwaj

14-Jul-07 4:49

Use dataview and thn set rowfilter to narrow down the result

Re: using datagrid in vb.net [modified]

Rharzkie14-Jul-07 20:23

Rharzkie

14-Jul-07 20:23

ok, i already know how, I saw the process and the codes in the internet...i used the "DISTINCT" in the query builder in Data Configuration Wizard... Then i put this codes in the search button:

OleDbDataAdapter2.SelectCommand.Parameters("subject").Value = ComboBox1.Text<br />
        DataSet21.Clear()<br />
        OleDbDataAdapter2.Fill(DataSet21)

but how, if i will going to put the codes in the combobox? Because what i want is if i will going to select a subject in the combobox, the students who enroll in that subject will automatically displayed in the datagrid without clicking the search button... Where i will going to put the codes above?

-- modified at 2:31 Sunday 15th July, 2007

Re: using datagrid in vb.net

TomGarth15-Jul-07 9:05

TomGarth

15-Jul-07 9:05

First of all, do yourself a favor and dump the DataGrid and use the DataGridView. You will be much happier with the added flexibility it has. Either way you can reset the contents by changing the DataSource, preferably to a DataView object.

Tom Garth
Developer
R. L. Nelson and Associates, Inc., Virginia

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