When does a query not use an index even if one exists?

When does a query not use an index even if one exists?

题目类型: 技术面试题

这是一道技术面试题，常见于澳洲IT公司面试中。

难度: hard

标签: interviewbit, dbms, topic-specific, database

参考答案摘要

A query may ignore an index if the optimizer thinks a full table scan is faster. This often happens when a large percentage of rows match the condition. Using functions on indexed columns can also pre...

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