query exists

@@ -100,3 +100,21 @@ func(s *SqlExcutor)Querys(v interface{})(total int,err error){
 	}
 	return
 }
+//查询是否存在
+func(s *SqlExcutor)QueryExists()(exists bool,err error){
+	var total int
+	o :=orm.NewOrm()
+	_,sqlCount,err :=s.Strings()
+	sqlCount=strings.Replace(sqlCount,"select count(0) ","select 1 ",1)
+	if !s.islimit{
+		sqlCount = sqlCount +" limit 1"
+	}
+	if err=o.Raw(sqlCount).QueryRow(&total);err!=nil{
+		return
+	}
+	exists = false
+	if total==1{
+		exists = true
+	}
+	return
+}