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Improve grammatical consistency (#774)

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Benjamin Yeh 2020-01-15 10:35:22 -08:00 committed by Hadley Wickham
parent 06fb600d84
commit 4708c0d8b5
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relational-data.Rmd
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@ -106,7 +106,7 @@ There are two types of keys:
each plane in the `planes` table.
* A __foreign key__ uniquely identifies an observation in another table.
For example, the `flights$tailnum` is a foreign key because it appears in the
For example, `flights$tailnum` is a foreign key because it appears in the
`flights` table where it matches each flight to a unique plane.
A variable can be both a primary key _and_ a foreign key. For example, `origin` is part of the `weather` primary key, and is also a foreign key for the `airport` table.