In 1.DELPHI operation access database (.mdb build files, compressed database)
the following code in WIN2K, D6, MDAC2.6 test passes,
the compiled program to run successfully under WIN98 second version without ACCESS environment.
Before // ComObj uses, the ActiveX
// declare the connection string
Const
sConnectionString = '= the Microsoft.Jet.OLEDB.4.0 Provider; the Data the Source =% S;'
+ 'the Jet OLEDB: Database PassWord =% S;';
//=============================================================================
// Procedure: GetTempPathFileName
// Author : ysai
// Date : 2003-01-27
// Arguments: (None)
// Result : string
//=============================================================================
function GetTempPathFileName():string;
//取得临时文件名
var
SPath,SFile:array [0..254] of char;
begin
GetTempPath(254,SPath);
GetTempFileName(SPath,'~SM',0,SFile);
result:=SFile;
DeleteFile(PChar(result));
end;
//=============================================================================
// Procedure: CreateAccessFile
// Author : ysai
// Date : 2003-01-27
// Arguments: FileName:String;PassWord:string=''
// Result : boolean
//=============================================================================
function CreateAccessFile(FileName:String;PassWord:string=''):boolean;
//建立Access文件，如果文件存在则失败
var
STempFileName:string;
vCatalog:OleVariant;
begin
STempFileName:=GetTempPathFileName;
try
vCatalog:=CreateOleObject('ADOX.Catalog');
vCatalog.Create(format(SConnectionString,[STempFileName,PassWord]));
result:=CopyFile(PChar(STempFileName),PChar(FileName),True);
DeleteFile(STempFileName);
except
result:=false;
end;
end;
//=============================================================================
// Procedure: CompactDatabase
// Author : ysai
// Date : 2003-01-27
// Arguments: AFileName,APassWord:string
// Result : boolean
//=============================================================================
function CompactDatabase(AFileName,APassWord:string):boolean;
//压缩与修复数据库,覆盖源文件
var
STempFileName:string;
vJE:OleVariant;
begin
STempFileName:=GetTempPathFileName;
try
vJE:=CreateOleObject('JRO.JetEngine');
vJE.CompactDatabase(format(SConnectionString,[AFileName,APassWord]),
format(SConnectionString,[STempFileName,APassWord]));
result:=CopyFile(PChar(STempFileName),PChar(AFileName),false);
DeleteFile(STempFileName);
except
result:=false;
end;
end;
//=============================================================================
// Procedure: ChangeDatabasePassword
// Author : ysai
// Date : 2003-01-27
// Arguments: AFileName,AOldPassWord,ANewPassWord:string
// Result : boolean
//=============================================================================
function ChangeDatabasePassword(AFileName,AOldPassWord,ANewPassWord:string):boolean;
//修改ACCESS数据库密码
var
STempFileName:string;
vJE:OleVariant;
begin
STempFileName:=GetTempPathFileName;
try
vJE:=CreateOleObject('JRO.JetEngine');
vJE.CompactDatabase(format(SConnectionString,[AFileName,AOldPassWord]),
format(SConnectionString,[STempFileName,ANewPassWord]));
result:=CopyFile(PChar(STempFileName),PChar(AFileName),false);
DeleteFile(STempFileName);
except
result:=false;
end;
end;
2.ACCESS used in SQL statements should pay attention to local and Skills to
the following SQL statements ACCESS XP query test by
built table:
the Create the Table Tab1 (
ID Counter,
the Name String,
Age Integer,
[a Date] DateTime);
tips:
auto-increment field declarations with Counter.
field called keywords in square brackets [] enclose, as the digital field names are also possible.
Indexing:
The following statement based on Date column Tab1 reusable index
Create Index iDate ON Tab1 ([Date ]);
After completion of the ACCESS field Date index properties displayed - at (duplicate).
The following statement Tab1 of establishing unrepeatable index on the Name column
Create Unique index iName oN Tab1 (Name );
after completion of the ACCESS attribute is displayed as the field Name index - has (without repeat).
the following statement removes just created two indexes
Drop index iDate oN Tab1;
Drop Index iName ON Tab1;
ACCESS and SQLSERVER UPDATE statement in the comparison:
SQLSERVER updated multiple-table UPDATE statement:
UPDATE Tab1
the SET a.name = b.name
the FROM Tab1 A, B Tab2
the WHERE a.id = b.ID;
same function SQL statements ACCESS should be
UPDATE Tab1 a, Tab2 b
the SET a.name = b.name
the WHERE a.id = b.ID;
namely: ACCESS UPDATE statement is not in the FROM clause, all references are listed in the table after the UPDATE keyword.
If the above example may not be a table Tab2, but a query, for example:
the UPDATE Tab1 a, (the Select ID, the From the Name Tab2) B
the SET a.name = b.name
the WHERE a.id = b.ID;
Accessing a plurality of different databases ACCESS - In use in SQL clauses:
the Select A *, B * Tab1 the From A, B Tab2 In 'Db2.mdb' = the Where a.id b.ID;..
The above SQL queries the current database Tab1 and db2.mdb all records (current folder) in Tab2 associated with the ID.
Cons - not external database with a password.
Added: see ugvanxk in a reply, you can use
Select * from [c: \ AA \ a.mdb; pwd = 1111] .table1;
ACCESS XP test passed
Access to other data sources in the ACCESS ODBC
embodiment the data query in the ACCESS SQLSERVER in
the SELECT * the FROM Tab1 the IN [ODBC]
[ODBC; Driver = the SQL Server; the UID = SA; the PWD =; Server = 127.0.0.1; the DataBase = Demo ;]
full parameter external data source attributes are:
[the ODBC; DRIVER = driver; SERVER = Server; DATABASE = Database; the UID = User; password = the PWD;]
which may DRIVER = driver registry
HKEY_LOCAL_MACHINE \ SOFTWARE \ ODBC \ ODBCINST.INI \
find the
guide data between heterogeneous databases see Sword of
http://www.delphibbs.com/delphibbs/dispq.asp?lid=1691966
ACCESS supports subqueries
ACCESS supports external connection, but not a complete external coupling, such as support
LEFT JOIN or RIGHT JOIN
but not
FULL OUTER JOIN or FULL JOIN
ACCESS date of inquiry
note: ACCESS date and time in the separator is # rather than quotation marks
Select * From Tab1 Where [Date] > # 2002-1-1 #;
in the DELPHI me with
SQL.Add (the Format (
'the Select the Where the From Tab1 * [a Date]> # S #%; ',
[DateToStr you (a Date)]));
ACCESS string may be separated by double quotes, but does not recognize SQLSERVER, so for convenience and compatibility migration
is recommended as a single quote string delimiter.
delphi ACCESS read a table name in the database
ADOConnection1.Close; ADOConnection1.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=' + Edit1.Text + ';Persist Security Info=False'; ADOConnection1.Open; ADOConnection1.GetTableNames(ComboBox1.Items); ComboBox1.ItemIndex := 0;
delphi connection and access ways
A connection mode .SQL database: Conditions: control name: AdoConnecion1, database name: the Sample, username: password SA: 123 , the database URL: native AdoConnection1.ConnectionString: = ' Provider = SQLOLEDB.1; Password = 123; the Persist Info = True Security; the User ID = SA; the Initial Cataog the Sample =; = Data Source. ' ; Adoconnection1.LoginPrompt: = False; Adoconnection1.Connected: = True; above code is coupled manner SQL database: the last one Data Source = , where the "." is a database in the machine, if the data in the other places, it will point to the IP address or server name. 2 coupled manner .ACCESS database: Condition: ADOConnection1, database name: Sample code: 123 , the database program accessing the file path is the root directory. Procedure TDataModule1.DataModuleCreate (Sender: TObject); var DbPath:String; begin DbPath:=ExtractFilePath(Application.ExeName)+'Sample.mdb'; Adoconnection1.ConnectionString:='Provider=Microsoft.Jet.OLEDB.4.0;Jet OLEDB:Database Password=123;Data Source='+DbPath+';Persist Security Info=false'; Adoconnection1.LoginPrompt:=False; Adoconnection1.Connected:=True; end;
Midas use to access the remote database access
Remote database access common approach is to use a large database that comes with the client tools, such as SQL Server and Oracle, and so with this tool. For such a small database with Access, this method can not be used, because Access does not provide such client tools. But we can achieve remote access Access database through MIDAS. MIDAS is a three-tier solution proposed by Delphi. The basic idea I provide access to a remote Access database methods used in MIDAS is built for remote access on the server side data module, and the client by MIDAS components to connect to it, and send SQL statements to the server on the client, the server performs return data sets to the client. Specific practices: Server-side server using ADO control to access the Access database, specifically ADOConnection control connection is established, ADOQuery perform related operations. Use the Data Access Controls ClientDataSet returned to the client dataset. And the above control on Remote Data Module vessel, for connection by the client. The following steps: 1 . Establishment of the Application. Which is named Form FormServer, Project called PrjServer; 2 . FileàNewàOther ..., New Items in the pop-up dialog box, select Multitier page, selecting the page in the Remote Data Module, is determined; 3In the pop-up Remote Data Module Wizard dialog box, filled in AccessServer coclass column, holding the Instancing and Threading Model default, i.e., between the threads independent of each other represents, after determining to generate a derived class AccessServer RemoteDataModule (at ViewàType Library that can view the detailed information of the class); 4 . a new file in the file folder named data as the program, the name under which placed a my.mdb Access database file with a name person table, the table has only two fields, respectively, and name Age, all texts; 5 put various controls on the AccessServer remote data module, the final results as shown below: server remote data module of each control related attributes the following table shows the effect of: the type of control relevant to the page attribute values action ADOConnection the ADO name ADOConnection1 connection Access file the ConnectionString Provider = Microsoft.Jet.OLEDB.4.0. 4.0 ; the Source the Data = \ Data \ my.mdb; = the Persist Security Info. False ADOQuery ADO name ADOQuery1 implementation of the relevant query Connection ADOConnection1 ClientDataSet the Data Access name DataSetProvider1 provide data interface to the client the DataSet ADOQuery1 Options. PoAllowCommandText to true Stardard6 . Compile and run the server program. Run the program that is registered with a MIDAS server, and only under the condition of a server program running to the next step of the client program development. The client in a way DCOM server-side connection, 1 Establishment Application. Which is named Form FormClient, Project called PrjClient; 2 placed on the respective control Form, the final results as shown below: The client interface associated with the role of each control properties shown in the following table: Control Type page belongs attribute values action Edit txtQuery name received query the Text SELECT * from Person the Button Stardard name btnQuery DCOMConnection the DataSnap name DCOMConnection1 through DCOM server connected ServerName PrjServer.AccessServer the ClientDataSet the Data Access name ClientDataSet1 issue SQL statements to the distal end, and obtain the data set the RemoteServer DCOMConnection1 the ProviderName DataSetProvider1 the DataSource the Data Access name DataSource1 as a data source controls present data in the DataSet ClientDataSet1 DBGrid the data controls name DBGrid1 Display the retrieved data set from the distal end the DataSource to DataSource1 Description: ServerName l DCOMConnection1 attribute is selected from the list, the list is a list of all registered servers MIDAS l ClientDataSet1 the ProviderName property is specified on a control server 3 in. Form Double-click on the button btnQuery, was added in its Click handler piece of code as follows: self.ClientDataSet1.Close; self.ClientDataSet1.CommandText: = self.txtQuery.Text; self.ClientDataSet1.Open; Note: If no is given returns the SQL statement, the last sentence was changed by the Open Execute. After the operation, results as shown below: The client running effect change the connection mode of the client in the above example are connected to a DCOM server mode, which typically only be used within a LAN. If you want to use in a wide area network, you can use Socket connected server. This is subject to make the following changes: 1 . On the server side running Delphi comes scktsrvr.exe program, the program Borland \ Delphi7 \ Bin \ folder 2Alternatively DCOMConnection control, change of the properties shown in the following table with the control on the client SocketConnection: control type relevant to the page attribute values action SocketConnection the DataSnap name SocketConnection1 through the Socket server connect the Address 127.0 . 0.1 (native) ServerName PrjServer.AccessServer the ClientDataSet Access the data RemoteServer SocketConnection1 sent to the remote SQL statement and obtain data sets Note: the default port SocketConnection is 211, which is the default port of scktsrvr. This should open the ports on the server firewall