diff --git a/backend/internal/handler/instance_extra.go b/backend/internal/handler/instance_extra.go
index 5c009ce..c359ef5 100644
--- a/backend/internal/handler/instance_extra.go
+++ b/backend/internal/handler/instance_extra.go
@@ -20,8 +20,12 @@ func AccessibleInstances(c *gin.Context) {
 	if role == "admin" || role == "dba" {
 		// admin/dba see all instances, filter by access_mode if needed
 		query := model.DB.Order("id")
+		// 注意：access_mode 存在两种历史写法——
+		//   前端「读」按钮写入 "read"（CreateInstanceForm），
+		//   另有 "readonly" 的历史值。两者都必须命中，否则选了「读」的实例
+		//   （尤其 MySQL）会被过滤掉，连 admin 都查不到。
 		if accessType == "readonly" {
-			query = query.Where("access_mode IN ? OR access_mode IS NULL", []string{"readwrite", "readonly"})
+			query = query.Where("access_mode IN ? OR access_mode IS NULL", []string{"readwrite", "readonly", "read"})
 		} else {
 			query = query.Where("access_mode IN ? OR access_mode IS NULL", []string{"readwrite", "write"})
 		}