Difference Between Primary index and Clustered index in AX Dynamics 365 There are two types of indexes 1. Unique or Primary 2. Clustered Index or Non-Unique 1. Primary index: Primary index identify records uniquely in any given table. It will not allow any duplicates records for the particular field in a table. The Primary Index (Unique index) can be create either on one field ( column) or multiple fields (columns). The data in Unique index should be unique and not null. Each Unique combination of primary key fields uniquely identifies one (and only one) record in the table. Primary Key must be Unique, There can be only one primary key for a table. But all unique indexes are not primary keys. Primary index used to retrieve data from data base , and used to organize both data store and other indexes for more efficient updating and faster access. 2. Clustered Index: Clustered or Non-Unique indexes are created for performance advantages . Clustered index ...