Activex Data Objects ADO

ActiveX Data Objects (ADO) is a high-level application programming interface (API) from Microsoft that provides a standardized way to access and manipulate data from a variety of sources. It is implemented as a set of Component Object Model (COM) objects, making it accessible from most Windows programming and scripting languages from its era.

ADO acts as an abstraction layer on top of OLE DB, which allows it to connect to any data source for which an OLE DB provider exists. This includes relational databases (SQL Server, Oracle), non-relational sources (file systems, email servers), and data accessed via an ODBC driver.

Core Objects

The ADO object model is relatively simple and consists of a few key objects:

• Connection: Represents an open connection to a data source. It is used to establish the session, configure connection strings, and manage transactions.
• Command: Represents a specific command you want to execute against the data source, such as a SQL statement, a stored procedure, or a table name.
• Recordset: This is the central object in ADO. It represents the entire set of records resulting from a query. You can use it to navigate through rows, and to add, update, or delete records. It functions like a cursor into the data.
• Parameter: Used to add parameters to a Command object, which is crucial for preventing SQL injection and calling stored procedures.
• Field: Represents a single column of data within a Recordset.

Example Usage (VBScript in classic ASP)

' Create ADO objects
Set conn = Server.CreateObject("ADODB.Connection")
Set rs = Server.CreateObject("ADODB.Recordset")

' Define the connection string and open the connection
conn.Open "Provider=SQLOLEDB;Data Source=myServer;Initial Catalog=myDB;User Id=myUser;Password=myPassword;"

' Define the SQL query and execute it
sql = "SELECT FirstName, LastName FROM Employees"
rs.Open sql, conn

' Loop through the recordset and display data
Do While Not rs.EOF
  Response.Write(rs("FirstName") & " " & rs("LastName") & "<br>")
  rs.MoveNext
Loop

' Clean up
rs.Close
conn.Close
Set rs = Nothing
Set conn = Nothing

This example demonstrates the typical workflow: create and open a connection, define and execute a query to populate a recordset, iterate through the records, and finally, close the connection and release the objects. This model, often referred to as Classic ADO, was the cornerstone of data-driven web and desktop applications on the Microsoft platform before the rise of .NET.