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Move exericse to better place 

Fixes #792
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Hadley Wickham 2021-04-18 09:41:05 -05:00
parent 023606e9aa
commit ef21701d2a
1 changed files with 7 additions and 7 deletions
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relational-data.Rmd
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@ -95,11 +95,6 @@ For nycflights13:
3. `weather` only contains information for the origin (NYC) airports.
If it contained weather records for all airports in the USA, what additional relation would it define with `flights`?
4. We know that some days of the year are "special", and fewer people than usual fly on them.
How might you represent that data as a data frame?
What would be the primary keys of that table?
How would it connect to the existing tables?
## Keys
The variables used to connect each pair of tables are called **keys**.
@ -165,7 +160,12 @@ For example, in this data there's a many-to-many relationship between airlines a
1. Add a surrogate key to `flights`.
2. Identify the keys in the following datasets
2. We know that some days of the year are "special", and fewer people than usual fly on them.
How might you represent that data as a data frame?
What would be the primary keys of that table?
How would it connect to the existing tables?
3. Identify the keys in the following datasets
a. `Lahman::Batting`,
b. `babynames::babynames`
@ -175,7 +175,7 @@ For example, in this data there's a many-to-many relationship between airlines a
(You might need to install some packages and read some documentation.)
3. Draw a diagram illustrating the connections between the `Batting`, `People`, and `Salaries` tables in the Lahman package.
4. Draw a diagram illustrating the connections between the `Batting`, `People`, and `Salaries` tables in the Lahman package.
Draw another diagram that shows the relationship between `People`, `Managers`, `AwardsManagers`.
How would you characterise the relationship between the `Batting`, `Pitching`, and `Fielding` tables?