How do indexes speed up searches?

Question

How do indexes help speed up data searches based on specific criteria?

If there is a table with six columns and none of them are indexed, the program should check all the rows of the table.

Indexing involves creating another separate table with two columns, an identifier and an index that you want to index.

What I don’t understand is how does this help the application to search faster? It does not read the entire table of six columns, but it still needs to read the entire table of two columns, right? Which has the same number of rows ...

Answer 1

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Answer 2

- -, ( B Tree).

- O(1) , O(log(n)).

, O(n).