Interview Bootcamp
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What are Indexes?

A shopping website has a users table with 10 million rows. When a user logs in, the database must find the one row with that user's email address.

Without any help, the database starts at the first row and checks every row until it has read all 10 million. On a busy website, this can take seconds, and it happens on every login.

With the right help, the same search reads only a few small blocks of data and finishes in a few milliseconds. That help is called an index. This lesson explains what an index is, how it makes queries faster, when it does not help, and what it costs.

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Yulian Stefanov

Yulian Stefanov

· 6 months ago

It would be useful if you could also cover a point of how performance is affected by indexes on columns that are meant to be used in searchbars. Since indexes resemble lookups that rely on exact match, a partial match would degrade the performance, no?

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