separate in four steps how to read databases

[avallecam]

after some changes, I think we can separate the steps here into four subtitles. This will increase the possibility to show extra info within each step.

1. connect with the database

show in a callout that this may look in real-life

# in real-life
db_con <- DBI::dbConnect(
  RSQLite::SQLite(), 
  host = "database.epiversetrace.com",
  user = "juanito",
  password = epiversetrace::askForPassword("Database password")
)

2. write a local data frame as a table in the database

...

3. read data from table

library(dbplyr)

# Take a reference of one table from the database
mydb <- tbl(src = db_con, "cases")

# Show the SQL queries translated
mydb %>% 
  dplyr::filter(confirm > 50) %>% 
  dplyr::arrange(desc(confirm)) %>% 
  dplyr::show_query()

# Pull all data down to a local tibble
mydb %>% 
  dplyr::filter(confirm > 50) %>% 
  dplyr::arrange(desc(confirm)) %>% 
  dplyr::collect()

4. close database connection

...

Originally posted by @avallecam in #70 (comment)