Add ColumnAs for 'SELECT col AS name' queries. (#24)

Add As helper for 'SELECT col AS name' queries

Clients could do this hackily before by manually passing "col AS name",
but it isn't clearly supported.

qb/select.go

@@ -115,6 +115,11 @@ func (b *SelectBuilder) Columns(columns ...string) *SelectBuilder {
 	return b
 }
 
+// As is a helper for adding a column AS name result column to the query.
+func As(column, name string) string {
+	return column + " AS " + name
+}
+
 // Distinct sets DISTINCT clause on the query.
 func (b *SelectBuilder) Distinct(columns ...string) *SelectBuilder {
 	b.distinct = append(b.distinct, columns...)

qb/select_test.go

@@ -28,6 +28,11 @@ func TestSelectBuilder(t *testing.T) {
 			B: Select("cycling.cyclist_name").Columns("id", "user_uuid", "firstname"),
 			S: "SELECT id,user_uuid,firstname FROM cycling.cyclist_name ",
 		},
+		// Add a SELECT AS column
+		{
+			B: Select("cycling.cyclist_name").Columns("id", "user_uuid", As("firstname", "name")),
+			S: "SELECT id,user_uuid,firstname AS name FROM cycling.cyclist_name ",
+		},
 		// Basic test for select distinct
 		{
 			B: Select("cycling.cyclist_name").Distinct("id"),