What are the three traditional database models? What are the disadvantages of each of them?

Relational model, mesh model, hierarchical model

1. The disadvantage of the relational model is that queries are not as efficient as the non-relational model. Therefore, in order to improve performance, user queries must be optimized, increasing the burden of developing a database management system.

2. The disadvantage of the mesh model is that the structure is more complex, and with the expansion of the application environment, the structure of the database becomes more and more complex, which is not conducive to end-user mastery.

Second, its DDL, DML language is complex and not easy for users to use. Used to link between records is realized through the access path, the application program to access the database must choose the appropriate access path. Therefore, the user must understand the details of the system's structure, increasing the burden of writing applications.

3. Disadvantages of Hierarchical Modeling

Many links in the real world are non-hierarchical, such as many-to-many links, a node has more than one biparent, etc. Hierarchical modeling does not naturally represent this type of linkage, and it can only be solved through the introduction of redundant data or the introduction of a virtual node

There are more limitations on insertion and deletion operations

Querying the children node must be done through a two-parent node

Expanded:

Advantages of hierarchical models

1, the model is simple, the description of the department with one-to-many hierarchical relationships is very natural, intuitive, easy to understand, which is the outstanding advantages of hierarchical databases

2, with the Hierarchical model of the application system performance is good, especially for those fixed and pre-defined links between the entities of the application, the use of hierarchical model to achieve, its performance is better than the relational model

3, hierarchical data model provides good integrity support.

References:

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Network Model_Baidu Encyclopedia Hierarchical Model_Baidu Encyclopedia ? Relational Modeling-Baidu Encyclopedia