Using ADO objects in Dephi programs to access ODBC data cont.

3. Other common objects (objects corresponding to Delphi):

ADODB. Field:tfield ADODB. Parameter:

Tpara ADODB. Error:edbengineerror

Adodb.command: No ADODB. Property: None

Here is an example of an application, listening to others say that you do not see the actual examples to experience. In this example, you will demonstrate how to use ADO objects to query a datasheet, add records, modify records, and delete record operations. Please see the comments in the program, if you have a bit of Delphi database programming experience, I believe it is not difficult to understand.

In our example the database used for Test.mdb, which has a datasheet for Wfjcommu, has five fields aname, portable, Tel, BP, postaddress, respectively, name, cell phone number, phone number, pager number and mailing address.

procedure Tform1.button1click (sender:tobject);


{*****************************************************


using ADO to operate an ODBC database in this program, you will create a temporary ODBC system data source, point to a msaccess database, and then display, add, modify, delete, and query the datasheet in it: Please include the Comobj cell in the uses statement


*****************************************************}


const{Some constant declarations, see adovbs.inc} in detail


{----CommandType constant description----}


adCmdUnknown = 0008;//unknown,


need system to judge, slow, default value


adcmdtext = 0001;//command statements such as SQL statements


adcmdtable = 0002;//Datasheet name


adCmdStoredProc = 0004;//Stored procedure name


{----CursorType constant description----}


adopenforwardonly = 0;//can only be accessed from the front backward one-way, the default value


adOpenKeyset = 1;//visible changes to the data by other users,


but additions and deletions to other users are not visible


adopendynamic = 2;//Other users are visible for additional modifications and deletions to the data


adOpenStatic = 3;//Other users are not visible for additional modifications and deletions to the data


{----LockType constant description---}


adlockreadonly = 1;//read-only, default value


adlockpessimistic = 2;//lock on a single record when modifying


adlockoptimistic = 3;//locks on a single record when updated after modification


adlockbatchoptimistic = 4;//record locks during mass update


var


aconnection, Arecordset variant;


Longinttemp:integer;


strtemp:string;


Intindex:integer;


begin


{Create a temporary ODBC data source, and use this DSN to establish a database connection to a msaccess database}


aconnection: = Createoleobject (ADODB. Connection);


Aconnection.open (driver={microsoft Access Driver


(*.mdb)};D bq=c:\inetpub\wwwroot\test);


{Set up a DataSet object and extract data from the datasheet}


Arecordset: = Createoleobject (ADODB. RecordSet);


Arecordset.open (wfjcommu,aconnection,


adopenstatic,adlockoptimistic,adcmdtable);


memo1.lines.clear;


Memo1.lines.add (the original contents of the ******** datasheet are as follows ********);


{Displays the domain name of each domain}


strtemp: =;


for Intindex: = 0 to Arecordset.fields.count-1 do


strtemp: = strtemp + arecordset.fields[intindex].name+;;


Memo1.lines.add (strtemp);


{Displays the contents of each field}


while does arecordset.eof do


begin


strtemp: =;


for Intindex: = 0 to Arecordset.fields.count-1 do


strtemp: = strtemp + arecordset.fields


[intindex].value+;;


Memo1.lines.add (strtemp);


arecordset.movenext;//move to the next bar, next


end;


{Add a record}


arecordset.addnew;//increased, Append


Arecordset.fields[aname]: = 1;


//Access
in a fieldbyname manner

arecordset.fields[portable]: = 2;


Arecordset.fields (2): = 3;


//Access
in Fields[index] mode

Arecordset.fields (3): = 4;


Arecordset.fields (4): = 5;


arecordset.update;//Update, Post


arecordset.movefirst;//move to the first one,


Memo1.lines.add (******** adds a recorded data table after the contents of the following ********);


{Displays the contents of each field}


while does arecordset.eof do


begin


strtemp: =;


for Intindex: = 0 to Arecordset.


fields.count-1 do


strtemp: = strtemp +


arecordset.fields[intindex].value+;;


Memo1.lines.add (strtemp);


arecordset.movenext;//move to the next bar, next


end;


{Modify last record}


Arecordset.movelast;


Arecordset.fields[aname]: = 11;


//Access
in a fieldbyname manner

Arecordset.fields[portable]: = 22;


Arecordset.fields (2): = 33;


//Access
in Fields[index] mode

Arecordset.fields (3): = 44;


Arecordset.fields (4): = 55;


arecordset.update;//Update, Post


arecordset.movefirst;//move to the first one,


Memo1.lines.add (******** modified the last record of the datasheet after the contents of the table are as follows ********);


{Displays the contents of each field}


while does arecordset.eof do


begin


strtemp: =;


for Intindex: = 0 to


arecordset.fields.count-1 do


strtemp: = strtemp +


arecordset.fields[intindex].value+;;


Memo1.lines.add (strtemp);


arecordset.movenext;//move to the next bar, next


end;


{Delete last record}


arecordset.movelast;//move to the end, last


arecordset.delete;//deleted, delete


arecordset.update;//Update, in Delphi do not need


arecordset.movefirst;//move to the first one,


Memo1.lines.add (******** deleted the last record of the datasheet after the contents of the table are as follows ********);


{Displays the contents of each field}


while does arecordset.eof do


begin


strtemp: =;


for Intindex: = 0 to Arecordset.fields.count-1 do


strtemp: = strtemp + Arecordset.


fields[intindex].value+;;


Memo1.lines.add (strtemp);


arecordset.movenext;//move to the next bar, next


end;


Arecordset.close; {Close Data Set}


{Query with SQL statements, query for records with the name "John"}


{Note that in SQL statements, strings should be included in single quotes}


arecordset.open (SELECT * FROM Wfjcommu


where aname = John,


Aconnection,adopenstatic,adlockoptimistic,


adCmdText);

The contents of
Memo1.lines.add (******** John are as follows ********);


memo1.lines.add (Total + inttostr (arecordset.recordcount) + stripe matching record);


{Show contents of individual fields}


while does arecordset.eof do


begin


strtemp: =;


for Intindex: = 0 to Arecordset.fields.count-1 do


strtemp: = strtemp + arecordset.fields


[intindex].value+;;


Memo1.lines.add (strtemp);


arecordset.movenext;//move to the next bar, next


end;


{Turn off Datasets and database connections}





Arecordset.close;


Aconnection.close;


end;

The above program is debugged by PWIN98+DELPHI3.0+PWS (Personal Web Server) 4.0. For more information about ADO objects, see the documentation for the ASP Help file or InterDev Help file or OFFICE2000.