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ERM and Indexing

Searching an ordered list of data is easier or more efficient than searching an unordered list. It is worth looking into the B-Tree (B stands for 'balanced' not 'binary'!) A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure.

Student friendly - what is an Index?

What is an Index

Indexes are used to quickly locate data without having to search every row in a database table every time a database table is accessed. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records. There are advantages and disadvantages to using an index. 

Suggested Video (if you're a developer!)