dialect/sql: append UNION before ORDER BY (#1761)

* fix: builder to append UNION before ORDER_BY

* gofmt builder_test.go

dialect/sql/builder.go

@@ -2320,6 +2320,9 @@ func (s *Selector) Query() (string, []interface{}) {
 		b.WriteString(" HAVING ")
 		b.Join(s.having)
 	}
+	if len(s.union) > 0 {
+		s.joinUnion(&b)
+	}
 	if len(s.order) > 0 {
 		s.joinOrder(&b)
 	}
@@ -2331,9 +2334,6 @@ func (s *Selector) Query() (string, []interface{}) {
 		b.WriteString(" OFFSET ")
 		b.WriteString(strconv.Itoa(*s.offset))
 	}
-	if len(s.union) > 0 {
-		s.joinUnion(&b)
-	}
 	s.joinLock(&b)
 	s.total = b.total
 	s.AddError(b.Err())