An API (application-program interface) lets a program interact with a database server. The application makes calls to:

• Connect with the database server.
• Send SQL commands to the database server.
• Fetch tuples of the result one-by-one into program variables.

Various tools:

• ODBC (Open Database Connectivity) — works with C, C++, C#, and Visual Basic; APIs such as ADO.NET sit on top of ODBC.
• JDBC (Java Database Connectivity) — works with Java.
• Embedded SQL.