When we sort the course records of the learning center, we can know the room which is available sometime. We can maintain the equipment of the room in the vacant time, so query function is very important.

Introduction of SQL sentence [6] . We can input command to operate the database. The grammar is as follows.

SELECT column name FROM table name. We can add other condition, such as where, order by [7] [8] . The column name is the property.

Example of SELECT sentence (query course information of room 505 and order by day of week).

Select sentence is as follows. SELECT * FROM room where 教室 = “教5楼505” order by 星期asc. Select is query. Room is the table name, 教室、星期is the attribute of the table. The data is order by day of week ascending. The result is shown as Figure 2.

In Figure 2, we can get the course records of “教五楼505”, and it’s sorted by day of week. It shows records of Monday, Tuesday and so on. The lesson time

column for Monday shows “第3, 4节”, “第1, 2节”, “第9 - 11节”, “第5, 6节”, “第7, 8节”. The information is unordered. It is used inconveniently.

Visual studio is a developing toolkit and is a developing environment pushed out by Microsoft Company. We design the program with MFC library. MFC means Microsoft Foundation Classes. When we create an MFC project, the project will generate 4 classes [12] [13] [14] (the view, the doc, the main Frame, the app). It is very convenient for programmer to design software in windows environment. The MFC frame defines the frame and offers the standard ways for user interface. The programer adds the functions in the frame.

CDocument: it is a document class [15] , the memory data communicates with database data with it. CView: it is view class. Users communicate with the memory data [16] with it and it includes interface and on draw function.

We add a combobox in the toolbar. The combox accesses the database and gets the course information. When the program is initiated, it adds the room number in the combobox. The user doesn’t need to type the room number.

CStringsel = “SELECT 教室 FROM room group by 教室”. The SQL sentence can query the room number and the records of same room number can generate one room number. The number is sorted.

The variable frame is the pointer of Mainframe in view class, frame->m_wndToolBar.m_combo_room. AddString (strRoom). Add the room number in the combobox, room number is queried form database. strRoom is the room number from database.

When user chooses room number, the room number will be the variable m_strobj Room. The program will operate invalidate (TRUE) to call the On Draw function, then the visual region will be refreshed [17] [18] .

1) Opening database

_ConnectionPtr m_pConnection; Define the variable to connect the database.

m_pConnection->Open(“Provider = Microsoft.Jet.OLEDB.4.0;Data Source = room.mdb”,”“,”“,adModeUnknown);

The second parameter DataSource is the database name.

(2) Generatingsqlsentenceautomatically according the user’s demand.

if(strcmp(m_strobjRoom,”全部”)==0)

{

sel.Format(“SELECT * FROM room order by 星期, 节次, 教室”);

}

else

{

sel.Format(“SELECT * FROM room where 教室=‘%s’ order by 星期,节次 “,m_strobjRoom);

}

According the user’s choice the program generates the SQL sentence. If the user chooses all the room, we query all the room in the course database. If the user chooses one room, the program generates the SQL sentence to query the course information for the room. The variable m_strobjRoom is the selected room number. When the user chooses all the room, the program generate the first SQL sentence. When the user chooses one room, the program generates the second SQL sentence.

3) Query data from the database and get result.

_RecordsetPtrm_pRecordset; Define the variable to receive data

m_pRecordset.CreateInstance(__uuidof(Recordset));

m_pRecordset->Open(_bstr_t(sel), //sel is the SQL sentence.

m_pConnection.GetInterfacePtr(), //get the database connection pointer

adOpenDynamic,

adLockOptimistic,

adCmdText);

Through opening operation, we can get result in variable m_pRecordset.

4) Traverse all the record

m_pRecordset->MoveNext(), move tothe next record.

m_pRecordset->adoEOF. The function checks whether the record is the last one. It always used in while circulation to traverse data [19] [20] .

There is a function called on draw in view class. The result is shown with the function. In order to make it easy to be found for user, the record in a day of week is set a color. For example the data of Monday is green, Tuesday is red.

pDC->SetTextColor(RGB(255,0,0)). The function set text color can set color for data. The value in RGB is different then the color is different.

pDC->TextOut(ptorigin.x+xnstep1,ptorigin.y,strClass). The function prints the records in the view. The variable ptorigin is the origin point. When the next record is shown, ptorigin. y is added a step length. When we traverse the data, all the records are shown in the view with different color.

The program includes several steps.

1) The program initiates MFC frame and generates the mainframe and the view.

2) The program Accesses the database and gets the course information. It adds the room number in the combobox.

3) The user chooses the choice in the combobox. The program generates SQL sentence.

4) The program opens the Room database, queries the information and gets result.

5) The result is shown in the view. The record’s color of different day is different. Close the database. If the user continues to query, go to step 3.

The flow chart is shown as Figure 5.

The program’s interface and the result is shown as Figure 6. The combobox is shown in the red ellipse. The user can choose room number in the combobox. The result is the course information of 教5楼312. The data’s color from Monday to Friday is different and course information is sorted by day of week, lesson time, it is easy find a record.