We can summarize that there is no insert anomalies in network model as in hierarchical model. Similarly a new part can be inserted who does not supplied by any supplier.Ĭonsider another case if supplier S 1 now starts supplying P3 part with quantity 100, then a new connector containing the 100 as supplied quantity is added in to the model and the pointer of S1 and P3 are modified as shown in the below. This is not possible in case of hierarchical model. The new supplier’s chain will simply consist of a single pointer starting from the supplier to itself.įor example, supplier S4 can be inserted in network model that does not supply any part as a new record occurrence with a single pointer from S4 to itself. Insert Operation: To insert a new record containing the details of a new supplier, we simply create a new record occurrence. Operations on Network Modelĭetailed description of all basic operations in Network Model is as under: Similarly, all connector occurrences for a given part are placed on a chain starting from the part and finally returning to the same part. The chain starts from a supplier and finally returns to the supplier. The database of Customer-Loan, which we discussed earlier for hierarchical model, is now represented for Network model as shown.Īll connector occurrences for a given supplier are placed on a chain. Each set is made up of at least two types of records: an owner record (equivalent to parent in the hierarchical model) and a member record (similar to the child record in the hierarchical model). In network database terminology, a relationship is a set. A network structure thus allows 1:1 (one: one), l: M (one: many), M: M (many: many) relationships among entities. Note that there are lateral connections as well as top-down connections. As shown below data can belong to more than one parent. The network model was evolved to specifically handle non-hierarchical relationships. The strict hierarchical arrangement is not possible here and the tree becomes a more generalized graph – a network. Suppose an employee works for two departments. In other words, it allows a record to have more than one parent. The main difference of the network model from the hierarchical model, is its ability to handle many to many (N:N) relations. The Network model replaces the hierarchical tree with a graph thus allowing more general connections among the nodes.