Interview Q&A / SQL & DBMS
SQL & DBMS interview questions
Joins, keys, normalisation, indexes and transactions for placement and backend interviews.
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- What is an index in a database and how does it speed up queries?
An index is a separate sorted structure, usually a B-tree, that maps column values to row locations. It lets the database jump to matching rows instead of scanning the whole table, at the cost of extra storage and slower writes.
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