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Connecting to Databases: Overview
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Most dataset components can connect directly to a database server. Once connected, the dataset communicates with the server automatically. When you open the dataset, it populates itself with data from the server, and when you post records, they are sent back the server and applied. A single connection component can be shared by multiple datasets, or each dataset can use its own connection.

Each type of dataset connects to the database server using its own type of connection component, which is designed to work with a single data access mechanism. The following table lists these data access mechanisms and the associated connection components:

Database connection components

Data Access Mechanism | Connection Component
Borland Database Engine (BDE) | TDatabase
ActiveX Data Objects (ADO) | TADOConnection
dbExpress | TSQLConnection
InterBase Express | TIBDatabase

Note: For a discussion of some pros and cons of each of these mechanisms, see Using Databases.
The connection component provides all the information necessary to establish a database connection. This information is different for each type of connection component:

- For information about describing a BDE-based connection, see Identifying the Database.
- For information about describing an ADO-based connection, see Connecting to a Data Store Using TADOConnection.
- For information about describing a dbExpress connection, see Setting up TSQLConnection.
- For information about describing an InterBase Express connection, see TIBDatabase.

Although each type of dataset uses a different connection component, they are all descendants of TCustomConnection. They all perform many of the same tasks and surface many of the same properties, methods, and events.

The following topics discuss many of these common tasks:

- Using Implicit Connections
- Controlling Connections
- Controlling Server Login
- Managing Transactions
- Working with Associated Datasets
- Sending Commands to the Server
- Obtaining Metadata

See Also

Designing Database Applications

Understanding Datasets

Using Data Controls

Working with Field Components

Creating and Using a Client Dataset

Working With ADO Components

Using Unidirectional Datasets

Using the Borland Database Engine

Using Provider Components

Creating Multi-tiered Applications: Overview

Using Decision Support Components

Using XML in Database Applications

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