From d98b6920874933d286f9a40a92ccb5f92b72d6f1 Mon Sep 17 00:00:00 2001 From: Bill Behrman Date: Wed, 13 Jul 2016 16:39:41 -0700 Subject: [PATCH] Initial commit --- relational-data.Rmd | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/relational-data.Rmd b/relational-data.Rmd index 3af796e..7d4e0e7 100644 --- a/relational-data.Rmd +++ b/relational-data.Rmd @@ -235,7 +235,7 @@ Graphically, that looks like: knitr::include_graphics("diagrams/join-outer.png") ``` -The most commonly used join is the left join: you use this whenever you lookup additional data out of another table, because it preserves the original observations even when there isn't a match. The left join should be your default join: use it unless you have a strong reason to prefer one of the others. +The most commonly used join is the left join: you use this whenever you look up additional data out of another table, because it preserves the original observations even when there isn't a match. The left join should be your default join: use it unless you have a strong reason to prefer one of the others. Another way to depict the different types of joins is with a Venn diagram: @@ -383,7 +383,7 @@ dplyr | SQL Note that "INNER" and "OUTER" are optional, and often omitted. -Joining different variables between the tables, e.g. `inner_join(x, y, by = c("a" = "b"))` uses a slightly different syntax in SQL: `SELECT * FROM x INNER JOIN y ON x.a = y.b`. As this syntax suggests SQL supports a wide range of join types than dplyr because you can connect the tables using constraints other than equality (sometimes called non-equijoins). +Joining different variables between the tables, e.g. `inner_join(x, y, by = c("a" = "b"))` uses a slightly different syntax in SQL: `SELECT * FROM x INNER JOIN y ON x.a = y.b`. As this syntax suggests SQL supports a wider range of join types than dplyr because you can connect the tables using constraints other than equality (sometimes called non-equijoins). ## Filtering joins {#filtering-joins}