Databases - Delphi Database Connections

Delphi is a great language, but, based on the help files, how to connect it to databases is not exactly clear.

On the tools pallette, there are 2 applicable tabs

The data controls are actually fairly simple to connect once the data access is configured. Just use the pick lists to set Data Source and Data Field, in that order.

Therefore, this page will discuss setting the Data Access components which are used to define Data Sources.

TTable -> TDataSource -> TQuery
TTable -> TDataSource -> TDBComboBox
TDatabase -> TTable -> TDataSource -> TDBComboBox
TTable connects to an ODBC database, a directory for Paradox tables,
or a TDatabase component.
DatabaseName, TableName

The pick list on TTable.DatabaseName lists available ODBC aliases
and TDatabase.DatabaseName values.

TDataSource - DataSet (TDataSet/TTable)
              Use this to handle record level processing.
              It keeps all related controls pointing to the same record.
              All data aware components must attach to a DataSource.

TDBComboBox - DataSource (TDataSource), DataField


First, Next, Last (and the like) are abstract members of TDataSet.
DataSet is a property of TDataSource.
TTable is a desendent of TDataSet.

Use TDatabase when you are using the BDE. Explicit declaration is not necessary unless you want access to the properties and methods at run time. The main advantage is the ability to disable the username/password request dialog box and/or to supply that data programatically.

If a TTable is used without explicitly associating it to an existing TDatabase, then an implicit TDatabase is created as necessary to control the connection.

Basic Procedure to See a Table's Contents

Place 3 components on a new (blank) Form. Set the following properties At this point, the table's data should be visible.

In order to step through the records, double click the TTable component (this opens the Fields editor dialog box) and use the VCR buttons to step through the records.


Use TDatabase if you want to connect to several tables in the same database, or if you want to suppress the annoying login prompt (You bet I want to :).

Note that when connecting directly to an MS Access database, the fully qualified path goes in the Params string list, not the the DatabaseName parameter.

I can not figure out how to get Microsoft Access Driver (*.mdb) to work.

Sequence to connect to an MS Access mdb file without using ODBC.

Field Components

Whenever a TTable (or other TDBDataSet based component) is placed on a form, Delphi automatically creates components (of base type TField) for all the available fields. By using the Fields editor dialog box (double click the TTable component), you can control which field components are created. In addition, you can explicitly create calculated and lookup fields.

There are a number of advantages to creating explicit field components.

You must use the Fields editor to add and remove presistent fields.


The Borland Database Engine (BDE) provides the ability to access various types of databases using the Data Access components. The main downside is that the BDE must be installed before your programs will work.

However, from the developer's point of view, the BDE based Data Explorer is an excelent tool that you should be very familiar with. (From inside Delphi, select Database / Explore) This tool will allow you to browse tables - you can see the data, determine the structure, and the like.

Run the BDE administrator to define aliases.


ADO allows you to develop database applications which do not need the BDE to run. You use MDAC instead. The main difference is that the MDAC is part of Windows 98 and beyond (ie, YOU don't have to install it).

Free on-line course

ADO is not part of Delphi 5 Professional - you must import it. Pay special attention to these installation instructions. Project / Import Type Library and select

However, the components do not have custom icons and there is a lack of help.


One alternative is to use KA Dao, a freeware component is available from,, or

The available help is pretty good, but it is not integrated into the Delphi help. Just open KADAO.HLP. Basic instructions are described via

In order to access an *.mdb file,

KADaoDatabase1 also has UserName, Password, and DatabasePassword which may need to be set. The difference between Password and DatabasePassword is not clearly explained.

There are 18 related dcu's - therefore, I keep them all with the original KADAO directory and link to it.

Running from a CD-ROM

Running software from a CD-ROM (a read only device) is fairly simple You can test the first step by right clicking the *.mdb file in Windows Explorer and setting its properties to ReadOnly.

Normally, when an *.mdb file is opened, a lock file (*.ldb) is created in the same directory as the *.mdb file. However, since a CD-ROM is read-only, you need to tell the jet database engine not to create the lock file - ReadOnly / Exclusive does this.

"per record" code

You can place "per record" code under either They both appear to work.


My Windows 98 system refuses to run the exe because it does not have a DAO license. A Windows 98 se systems has no problem.


dbExpress is supposedly the replacement for the BDE (which is no longer supported). Using it requires loading various *.dll files on the client machines.

Delphi, dbExpress And MySQL explains how to use dbExpress to connect to MySQL. It also provides a warning - dbExpress: Delphi 6 Versus Delphi 7 - not to run both Delphi 6 and Delphi 7 applications on the same machine when accessing Firebird databases - the dbExpress *.dll's are not compatible and will cause errors.


Firebird is an open source (free) version of Borland's Interbase SQL database engine. There are several different ways to access tables

Using the Interbase Components

In order to access an *.gdb file,

If you edit some parameter and no data is displayed, check IBDatabase1.Connected, IBTransaction1.Active, and IBTable1.Active, in that order. (Actually, just setting IBTable1.Active to True will automatically set the others.)

In order to automatically connect to a Firebird database, set the following

To connect to the Interbase example database distributed with Delphi, set IBDatabase1.DatabaseName to

According to a newsgroup post, TIBTable should never be used with Client/Server applications - use IBDataset instead. (They are both based on TIBCustomDataSet) This partly because a TIBTable.Refresh will not return inserted items and IBDataset.Refresh will (I guess that the query is reexecuted).


In order to access a Firebird database via ODBC, you must first define an ODBC connection (DSN). Select Control Panel / Administrative Tools / Data Sources (ODBC) / System DSN / Add... Then select the Interbase driver. In the dialog box, only these 2 fields are important. Once you have created the DSN, you can test it by re-opening the definition (double click or select Configure...), entering the Username and Password, and clicking Test Connect. Unfortunately, this always failed on my Windows XP system.

In order to access an *.gdb file via ODBC/ADO (I was never able to get this to work),

I got lots of errors related to the Workgroup information file, but, of cource, there is no help on what that may mean. I assume that this is related to the ODBC failure above.


efg's Computer Lab provides DBF Files -- With or Without ADO
This provides very detailed step by step instructions on how to connect to an *.dbf file using both a TTable component and Borland's ADO components. Both examples use Data Modules.

Author: Robert Clemenzi -
URL: http:// / user / clemenzi / technical / Databases / Delphi / Database_Connections.html