The three generations of DBMS are as follows:
• The first generation of DBMS is the hierarchal network or CODASYL model.
• The hierarchal network was developed by the Information Management System.
• The CODASYL model was developed by the Integrated Data Store.
• CODASYL is a group of people who are responsible for standardizing the COBAL.
• Searching is not possible in CODASYL which is the major drawback.
• The second generation of DBMS is the relational model.
• Representation of data in the form of tables is known as relational data model.
• A table is generally a combination of rows and columns.
• Columns can be called as attributes and rows can be called as records.
• In a relational data model the schema for a relation specifies its name, the name of each field and also the type of each field.
• The third generation of DBMS is the object relational DBMS model and the object-oriented DBMS.
• This ORDBMS adds a new object storage capability to the relational system at the core of modern information systems.
• Here, the objects as well as the classes are directly supported by the database schemas.