Covering indexes allow data storage within the index itself while sparse indexes exclude documents that do not contain the missing field.

Covered索引允许在索引本身里存储数据，而Sparse索引则会排除掉不包含索引字段的文档。

youdao

The index is a combination of three sub-indices covering wealth, health and education.

该指数由3个次指标组成，涵盖了财富，健康和教育领域。

youdao

The answer to the question as stated in your subject line in general is no. Because you generally would much prefer to have the narrowest covering (probably non-clustered) index.

这个问题的答案所你的主题一般是否定的。因为你通常可能更倾向于有窄覆盖(可能非集群)指数。

youdao

Earlier this month, the index covering the Mumbai exchange touched levels not seen since February 2001, having climbed by more than 50% since April.

ECONOMIST: India's economy

Japan accounts for the largest country weighting in the MSCI EAFE (Europe, Australia, Far East) index, a global stock index covering more than 20 countries.

FORBES: When All Else Fails, Go Long

The ISM Non-Mfg Index, covering the services sector, also declined in March.

FORBES: Stock Market Warning Signs Becoming Ominous