r-sql.md

layout	element	title	language
page	notes	Integrating R and SQL	R

Remember to

• download portal_mammals.sqlite.
• open portal_mammals.sqlite in SQLite Manager.
• make sure the copy you are going to use in class does not have the SpeciesCounts table or view.

• We've already seen how to connect to databases using dplyr.
• What if we want to work outside of a dplyr context?
• Use DBI and RSQLite.
  • also other database management systems plugins

Connect

library(DBI)
library(RSQLite)
portalDB <- "portal_mammals.sqlite"
conn <- dbConnect(SQLite(), portalDB)

Check out database structure

dbListTables(conn)
dbListFields(conn, "plots")
dbListFields(conn, "surveys")

Run queries

query <- "SELECT genus, species, COUNT(*)
          FROM surveys JOIN species
          ON surveys.species_ID = species.species_ID
          GROUP BY genus, species;"
species_counts <- dbGetQuery(conn, query)

Do [Exercise 1 - Connect and Query]({{ site.baseurl }}/exercises/R-sql-connect-and-query-R).

Write new information to database

Show the original portal_mammals.sqlite in SQLite Manager.

• Write as a table

dbWriteTable(conn, "SpeciesCounts", species_counts)
dbListTables(conn)

Show SpeciesCounts table in portal_mammals.sqlite.

• Write as a view

viewquery <- paste("CREATE VIEW SpeciesCounts AS", query)
dbSendQuery(conn, viewquery)

Show the SpeciesCounts view in portal_mammals.sqlite.

Do [Exercise 3 - Export to Database]({{ site.baseurl }}/exercises/R-sql-export-to-database-R).

Assign remaining exercises.