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Indexing in SQL

Let us understand how normal (without indexing) query runs. It basically traverse each rows one by one and when it finds the data it returns.
Without Index:
Without indexingSo suppose query is to find 50 , it will have to read 49 records as a linear search.
With Index:
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When we apply indexing, the query will quickly find out the data without reading each one of them just by eliminating half of the data in each traversal like a binary search. 

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