Interview Q&A / SQL & DBMS
SQL & DBMS interview questions
Joins, keys, normalisation, indexes and transactions for placement and backend interviews.
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- Why might the database ignore an index on a column?
Common reasons are wrapping the column in a function, a leading wildcard in LIKE, a type mismatch, a condition that matches most rows, or outdated statistics. The optimizer then prefers a full scan.
IntermediateQuick answer1 min read