Indexing is a way to optimize the performance of a database by minimizing the number of disk accesses required when a query is processed. It is a data structure technique that is used to quickly locate and access the data in a database. Indexes are created using a few database columns.

What Does Indexing Do?

Indexing is the way to get an unordered table into an order that will maximize the query’s efficiency while searching. For example, the table below represents a table in a fictional data source, that is completely unordered. https://prnt.sc/u1DA-SN2Q_Pp  If we were to run the following query:

SELECT
  company_id,
  units,
  unit_cost
FROM
  index_test
WHERE
  company_id = 18

The database would have to search through all 17 rows in the order they appear in the table, from top to bottom, one at a time. So to search for all of the potential instances of the company_id number 18, the database must look through the entire table for all appearances of 18 in the company_id column. With an index on the company_id column, the table would, essentially, “look” like this: https://prnt.sc/_Waf_AkDID0y Now, the database can search for company_id number 18 and return all the requested columns for that row then move on to the next row. If the next row’s comapny_id number is also 18 then it will return the all the columns requested in the query. If the next row’s company_id is 20, the query knows to stop searching and the query will finish.