Without an index sarg, an index scan will use the index to access the data, but will return every key in the index.

没有索引sarg时，索引扫描将使用索引访问数据，但是会返回索引中的所有键。

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The UK population is estimated at 180, 000 according to the Surrey Amphibian and Reptile Group (SARG).

BBC: Slough Crossrail workers discover sleeping snakes