Techincal Diary

SQL Server 2008 wildcards used in Query

2011-11-02T01:16:00.001-07:00

I have just learn some useful wildcards for SQL Server 2008 recently.

( _ ) Underscore Wildcard character

Underscore wildcard character can be used to limit the search result for an exact number of characters.

Example: SELECT * FROM Employee WHERE LastName like 'Li_' will return all employees whose LastName like 'Lin' or 'Lim' but not 'Linux'.

(-) Wildcard Character

- wild card character can be used to limit the search results for character within a range.

Example: SELECT * FROM Employee WHERE LastName like '[A-E]%' will return all employees whose last name started with A to E.

(^-) Wildcard Character

^- wild card character can be used to limit the search results for character outside a range.

Example: SELECT * FROM Employee WHERE LastName like '[^A-E]%' will return all employees whose last name NOT started with A to E.

Calcuating Eigen object with OpenCV

2010-12-03T00:24:00.000-08:00

I am using OpenCV to develop a computer vision application. Last night, I woke up in the middle of the night and tried to debug the method which I do PCA (Principal Component Analysis) and calculating the EigentObject.

But when I run cvCalcEigenObject() method from the cvaux library, the application crashed with memory error. I tried to solve this problem for a few hours and finally find out that images that I used for calculation of Eigen object have different height and width (in pixels). It should be same size and width to run the cvCalcEigenObject() correctly. I tried to adjust the image size and the problem was gone without changing a single line of code.

Reading Configuration file from DLL

2010-12-03T00:13:00.000-08:00

If you want to read the configuration file from DLL, it should be under the same folder with "exe". So when you run the main application which called DLL, it can read the setting from the configuration file.

http://social.msdn.microsoft.com/Forums/en-US/wcf/thread/c97b709d-d04c-4fd1-95e4-d8eb3a1ac477/

Mapping Network Drive to Local Folder

2010-11-28T21:31:00.001-08:00

To Map a network drive letter to local folder, I found that I can use the following command at the command prompt.

subst [Drive]: C:\FolderName

For example, I can map "C:\Temp" folder to K: drive using the command.

subst K: C:\Temp

TCPClient.Connected property

2010-06-18T10:25:00.000-07:00

I was writing TCP server application which is written in Microsoft Visual C# 2008. I need to accept TCPClient which sent connection request to my server. One of the features that I need to implement is to keep track of the client status whether it was connected to my server or it had already been disconnected from my server.

I found the TCPClient.Connected property in .NET and so I used it to keep track of the client status. But it was totally unreliable. I still could receive TCPClient.Connected property as true even if the client had already been shutdown. I scratched my head to find out what was the cause of the problem. As usual, I searched Internet to find out if other people had encountered same problem before.

To my surprise, TCPClient.Connected property was not actually reflecting the current status of the client. It would only show the status that last time when the server was trying to communicate to client. So it can consider unreliable.

I hate to do it but I need to implement additional logic to keep track of my client. I need to keep record of the time when the client was trying to connected to my server and compare those value with timeout.

Raising Event from DLL

2010-06-18T10:13:00.000-07:00

I am currently developing a new software for a new machine. I need to interface my .NET program to COM DLL to control the hardware. I was writing one DLL for common methods which I can reuse in future applications. I was also writing Windows Application for the methods specific to that machine.

The COM DLL that I am calling from my DLL is written by "ADLink" technology which interfaced to Motion Control module and I/O modules. I was trying to drive servo motors from that DLL. I could successfully drive the servo but it took 10 seconds for my Windows application to receive motion complete event from Servo. I was trying to troubleshoot servo and motion control card but I have no clue what was actually happening.

Finally, I found the problem when I carefully log every line of code in my program. It took 10 seconds to receive the event from DLL to my Windows Application. I tried to move the event raising to Windows application and the problem was solved.

Unlocking HR and OE Schema in Oracle Database

2009-07-10T00:21:00.000-07:00

We can use SQL * Plus to unlock OE and HR schema come along with Oracle Database later than version 9i as follow;

ALTER USER hr IDENTIFIED BY hr ACCOUNT UNLOCK;
GRANT CONNECT, RESOURCE to hr;

ALTER USER oe IDENTIFIED BY OE ACCOUNT UNLOCK;
GRANT CONNECT, RESOURCE to OE;

Default password for HR is "hr".

How to Disconnect from Network folder

2009-05-19T23:48:00.000-07:00

There is a network directory like "\\ABCD\\EFGH" in my office server that I used to access. I need to log-in to the directory for only first time. Now I want to disconnect it from the server because I want to test my program which need to access network directory with user name and password. So I find a way to disconnect from server. I found out as follows:

Click Start and open Run
In that window type: control userpasswords2
Press OK
in the next window go to the secon tab on top, named: Advanced
and from there open: Manage Passwords
There you should see if there is a password stored for the address that you have mentioned
If yes then delete it and close the windows with OK
try to connect again to that address, it should prompt for authentication. Do not check the Remember option...

(Source: http://en.kioskea.net/forum/affich-35879-to-disable-auto-login-network-share-folders)