I want to find a use online.
CDAO *
Classes come from the data sheet or write data, but I didn't get any clues. Now you have completed this feature, from a Microsoft
ACCESS
file(
.Mdb
) Fast, dynamic, and simple creation
/
Write
/
Read data
. Our example is a dialog-based program.
Design our interface
In order to build our database interface, we should first we should be in the project.
STDAFX.H
Add to
Afxdao.h
statement of.
We will use two classes
CDaoDatabase
with
CDaorecordset
In the program, you need to use these two classes to construct them:
CDaodatabase Database; CDaorecordSet Recordset (& Database);
Create our database file
If we are dynamically created
ACCESS
Document, we don't need to use
CDaoDatabase :: open ()
,because
Create ()
The function will automatically open our connected database:
CString lpszfile = "c: //database.mdb"; Database.create (lpszfile);
Open an existing database file
Database.open (lpszfile);
Very good, now we have successfully connected to a database, then we can write data to the data table. Here first introduces the structure of some data tables, which is good for you to develop database development in the future.
A data table is a series of data sheets. You can use multiple data tables in a database file, each data sheet from row
(ROWS)
Column
(Column)
composition. Corresponding to the value of a row and column is called fields (
Field
). Below is an illustration of a standard data sheet:
Let us return to the subject. We first need to create a data sheet in our database file. What to do?
?
We create one by creating one
SQL
Execute a string to tell our database instance to execute it, for example
:
CString Sqlcmd = "Create Table MyTable (Name Varchar (20), Age Varchar (3));"; Database.execute (SQLCMD);
Above
SQL
Commands created a new name in our database file
MyTable
Data table. It has two columns, one is
Name
, One is
AGE
.
Name
Column data limit
20
Character,
AGE
Column data limit
3
Character. Very simple.
Note: You cannot create the same name data sheet in a file, unless you first use the correct
SQL
String call
EXECUTE ()
Function, delete this table.
Add data in a new data sheet
use
CDaorecordset
Example Open our database, when we create it for the first time, we will have one
CDaoDatabase
The pointer of the instance is now connected. In order to open our record and write data, we do the following code:
recordset.Open (AFX_DAO_USE_DEFAULT_TYPE, "SELECT * FROM MyTable", 0); database.Execute ( "INSERT INTO MyTable (Name);"); database.Execute ( "INSERT INTO MyTable (Age);"); recordset.AddNew ( ); RecordSet.setfieldValue ("name", "chris"); recordset.setfieldValue ("age", "13"); recordset.Update (); recordset.movenext (); recordset.addNew (); recordset.SetfieldValue "Name", "Joe"); RecordSet.SetfieldValue ("Age", "20"); RecordSet.Update (); Let's see the meaning of the above code:
1.
We use
SQL
command
Select * from myTable
Open the record instance. This means that the open function will get
MyTable
All data available in the data table, whether it is written or read.
2.
use
SQL
String call
EXECUTE ()
To join two new columns in the data sheet.
3.
transfer
AddNew ()
Allow us to join a new data
4.
Twice
SetFieldValue
The data is added to the two columns on the same line three, respectively.
5.
transfer
Update ()
Update the data of the data table.
6.
transfer
MoveNext ()
Move the record pointer to the next blank, repeat the method of adding the data above.
The above is a method of adding data to the data sheet. Here we describe how to read data from the data table. This part is also quite simple and easy to understand.
CDAORECORDSET :: getfieldvalue ()
The function has two parameters, one is the name of the column we want to get the data, which corresponds to the current location of the record pointer, we can move it freely by calling the following functions:
:: seek (); :: movefirst (); :: movenext (); :: moveprev () ;:: movelast ();
The second parameter is one
Colevariant
Example,
Colevariant
Be a base based on
COM
Object. Our field data will be stored in this object, but converting this storage object to we can identify
Cstring
The variable is what we need, the following code is to complete this work:
Colevariant olevar;
Confirm our
CDaorecordset
The instance has been opened, we call
While (! recordset.iseof ()); {olevar.changtype; RecordSet.GetfieldValue ("name", olevar); cstring strdata = (lpcstr) olevar.pbstrval; // code for Inserting Data Into a listbox , for exampleXT.MOVENEXT ();
Changeetype ()
Method
Colevariant
Instance conversion to
BSTR
(A hypothyroidistic string format). then we
PBSTRVALUE
Method conversion to
Cstring
We can use it in any way. These can be reused using the end of the identity record in the data table.
I believe that the above instructions are helpful to you.
