Add support for Group By statements (#2)

Thanks!

Author: alexsante

select.go

@@ -39,6 +39,8 @@ type QueryStatement struct {
 	hasRowcount         bool
 	rowcount            int
 	useRowcount         bool
+	hasGroupBy          bool
+	groupBy             string
 }
 
 // NewQueryStatement returns a new instance of the select statement
@@ -110,6 +112,15 @@ func (q *QueryStatement) Where(where string) *QueryStatement {
 	return q
 }
 
+// GroupBy will append a group by statement to the query
+func (q *QueryStatement) GroupBy(groupBy string) *QueryStatement {
+	if len(groupBy) > 0 {
+		q.groupBy = groupBy
+		q.hasGroupBy = true
+	}
+	return q
+}
+
 // And continues to add to the where statement
 func (q *QueryStatement) And(param string) *QueryStatement {
 	if len(param) > 0 {
@@ -241,6 +252,11 @@ func (q *QueryStatement) Assemble() (string, error) {
 		}
 	}
 
+	if q.hasGroupBy {
+		sql.WriteString(" GROUP BY ")
+		sql.WriteString(q.groupBy)
+	}
+
 	if q.hasOrderBy {
 		sql.WriteString(" ORDER BY ")
 		sql.WriteString(q.orderby)