Merge pull request #23 from eduardpeters/typos

Fix typo in Constraints lesson text

Author: dtauer

lessons/04-joins-and-constraints/E-constraints.md

@@ -6,7 +6,7 @@ You actually already know what constraints are and have used them not once but T
 
 A constraint is just a constraint you put around a column. For example, NOT NULL is a constraint we've used for our primary keys. You always need a primary key.
 
-UNIQUE is another constraint that dictates that this column must be unqiue amongst all other columns. Ever wonder how an app can tell you so quickly if an email or a user name is taken so quickly? They likely use a UNIQUE constraint on those two columns. They should. PRIMARY is another such constraint.
+UNIQUE is another constraint that dictates that this column must be unique amongst all other columns. Ever wonder how an app can tell you so quickly if an email or a user name is taken so quickly? They likely use a UNIQUE constraint on those two columns. They should. PRIMARY is another such constraint.
 
 We also added a constraint on recipe_ingredients that every row must have a unique combination of recipe_id and ingredient_id. We could have added an additional primary, incrementing, unique ID but what would we use that for? To me at this moment it doesn't serve a purpose so we can just use the other two as a unique key. This is common for these sorts of many-to-many connecting tables.