Update databases.Rmd

vignettes/databases.Rmd

@@ -18,7 +18,7 @@ As well as working with local in-memory data like data frames and data tables, d
 
 Since R almost exclusively works with in-memory data, if you do have a lot of data in a database, you can't just dump it into R. Instead, you'll have to work with subsets or aggregates. dplyr aims to make this task as easy as possible. If you're working with large data, it's also likely that you'll need support to get the data into the database and to ensure you have the right indices for good performance. While dplyr provides some simple tools to help with these tasks, they are no substitute for a local expert.
 
-The motivation for supporting databases in dplyr is that you never pull down the right subset or aggregate from the database on your first try. Usually you have to iterate between R and SQL many times before you get the perfect dataset. But because switching between languages is cognitively challenging (especially because R and SQL are so perilously similar), dplyr helps you by allowing you to write R code that is automatically translated to SQL. The goal of dplyr is not to replace every SQL function with an R function; that would be difficult and error prone. Instead, dplyr generates `SELECT` statements, the SQL you write most often as an analyst.
+The motivation for supporting databases in dplyr is that you never pull down the right subset or aggregate from the database on your first try. Usually you have to iterate between R and SQL many times before you get the perfect dataset. But because switching between languages is cognitively challenging (especially because R and SQL are so perilously similar), dplyr helps you by allowing you to write R code that is automatically translated to SQL. The goal of dplyr is not to replace every SQL function with an R function; that would be difficult and error prone. Instead, dplyr only generates `SELECT` statements, the SQL you write most often as an analyst.
 
 To get the most out of this chapter, you'll need to be familiar with querying SQL databases using the `SELECT` statement. If you have some familiarity with SQL and you'd like to learn more, I found [how indexes work in SQLite](http://www.sqlite.org/queryplanner.html) and [10 easy steps to a complete understanding of SQL](http://tech.pro/tutorial/1555/10-easy-steps-to-a-complete-understanding-of-sql) to be particularly helpful.