diff --git a/vql.go b/vql.go
index 357093b..90a238f 100644
--- a/vql.go
+++ b/vql.go
@@ -19,9 +19,9 @@ func NoParameConvertFunc(vTable string, convertSql string) *VirtualTable {
 }
 
 type VirtualTable struct {
-	MappingTableName string //example: user(db:db1,id:1)
-	//限定条件
-	SqlConvert VirtualQlConvert
+	MappingTableName string   //example: user(db:db1,id:1)
+	ArgNames         []string //example: [db,id]
+	SqlConvert       VirtualQlConvert
 }
 
 func parseTableName(tableNameExpression string) (tableName string, args map[string]string, err error) {
@@ -120,8 +120,10 @@ func (vql *VirtualQL) convert(query *Query, val map[string]interface{}) error {
 			val = make(map[string]interface{})
 		}
 
-		for k, v := range args {
-			val[k] = v
+		for k := range vtable.ArgNames {
+			if args[vtable.ArgNames[k]] != "" {
+				val[vtable.ArgNames[k]] = args[vtable.ArgNames[k]]
+			}
 		}
 
 		convertSql, err := vtable.SqlConvert(val)