There are three models:-
(a) Hierarchical Model: It assigns records to different levels of hierarchy. A lower level record is called the child and the higher level is called the parent. Data redundancy is the disadvantage of this model.
(b) Network Model :
It is similar to hierarchical model, but each child record can have more than one parent record. This model eliminates the redundancy encountered in the hierarchy model, but it has a high degree of complexity. It was introduced by CODASYL-DBTG in 1971.
(c) Relational Model :
It is based on the concept introduced by E F Godd. It composed of one or more tables. Here tables are called relations, rows are called tuples and the columns are called attributes. It has no data redundancy and complexity. So this is the best model.
