OLE DB (Object Linking and Embedding, Database, sometimes written as OLEDB or OLE-DB) is an API designed by Microsoft for accessing data from a variety of sources in a uniform manner.
It is a set of interfaces implemented using the Component Object Model (COM); it is otherwise unrelated to OLE. It was designed as a higher-level replacement for, and successor to, ODBC, extending its feature set to support a wider variety of non-relational databases, such as object databases and spreadsheets that do not necessarily implement SQL.
OLE DB separates the data store from the application that needs access to it through a set of abstractions that include the datasource, session, command and rowsets. This was done because different applications need access to different types and sources of data and do not necessarily want to know how to access functionality with technology-specific methods. OLE DB is conceptually divided into consumers and providers. The consumers are the applications that need access to the data, and the provider is the software component that implements the interface and therefore provides the data to the consumer. OLE DB is part of the Microsoft Data Access Components (MDAC) stack. MDAC is a group of Microsoft technologies that interact together as a framework that allows programmers a uniform and comprehensive way of developing applications for accessing almost any data store. OLE DB providers can be created to access such simple data stores as a text file and spreadsheet, through to such complex databases as Oracle, SQL Server and Sybase ASE. It can also provide access to hierarchical datastores such as email systems.
However, because different data store technologies can have different capabilities, OLE DB providers may not implement every possible interface available to OLE DB. The capabilities that are available are implemented through the use of COM objects - an OLE DB provider will map the data store technologies functionality to a particular COM interface. Microsoft describes the availability of an interface as "provider-specific," as it may not be applicable depending on the database technology involved. Note also that providers may augment the capabilities of a data store - these capabilities are known as services in Microsoft parlance.
