Update 15-database.mkd

Little typo- and grammar mistakes :)

Author: catwarner

book3/15-database.mkd

@@ -417,7 +417,7 @@ INSERT INTO Artist (name, eyes)
 
 \index{primary key}
 Now we have two tables but we need a way to *link* rows in the two tables.
-To do this, we need why we call 'keys'.  These keys will just be integer numbers
+To do this, we need what we call 'keys'.  These keys will just be integer numbers
 that we can use to lookup a row in different table.  If we are going to make
 links to rows inside of a table, we need to add a *primary key* to the rows in the
 table.  By convention we usually name the primary key column 'id'.  So our
@@ -478,7 +478,7 @@ New York|25|Frank Sinatra|blue
 While it might seem a little clunky and your instincts might tell you that
 it would be faster just to keep the data in one table, it turns out the
 the limit on database performance is how much data needs to be scanned
-when retrieving a query.  While they details are very complex, integers
+when retrieving a query.  While the details are very complex, integers
 are a lot smaller than strings (especially Unicode) and far quicker to
 to move and compare.
 
@@ -497,7 +497,7 @@ of our data model.
 
 \index{Crow's Foot diagrams}
 While there are many graphical representations of data models, we will use
-one of the "classic" appraches, called "Crow's Foot Diagrams" as shown in Figure \ref{figvrbo2m}.
+one of the "classic" approaches, called "Crow's Foot Diagrams" as shown in Figure \ref{figvrbo2m}.
 Each table is shown as a box with the name of the table and its columns.  Then where there
 is a relationship between two tables a line is drawn connecting the tables with
 a notation added to the end of each line indicating the nature of the relationship.
@@ -877,10 +877,10 @@ for many courses and a course will have many users on its roster.
 
 It is pretty simple to *draw* a many-to-many relationship as shown in Figure \ref{figm2m}.
 We simply draw two tables and connect them with a line that has the "many" indicator on both
-ends of the lines.  The problem is how to *implement* the raltionship using primary keys and
+ends of the lines.  The problem is how to *implement* the relationship using primary keys and
 foreign keys.
 
-Before we explore how we implement many-to-many relationships, lets see if we could hack
+Before we explore how we implement many-to-many relationships, let's see if we could hack
 something up by extending a one-to many relationship.
 
 ![A Many to Many Relationship\label{figm2m}](height=1.5in@../images/many-to-many)