diff --git a/lib/TclUpdates/SQLiteWriter.php b/lib/TclUpdates/SQLiteWriter.php
index 0852c23..061e160 100755
--- a/lib/TclUpdates/SQLiteWriter.php
+++ b/lib/TclUpdates/SQLiteWriter.php
@@ -14,6 +14,7 @@ class SQLiteWriter
         if ($this->pdo === false) {
             return $sqlerror;
         }
+        $this->pdo->exec('PRAGMA foreign_keys=on;');
     }
 
     private function insertArray($table, $data, $replace = false)
@@ -75,6 +76,8 @@ class SQLiteWriter
                 'sha1' => $file_arr['file_sha1'],
                 'file_name' => $file_arr['file_name'],
                 'file_size' => $file_arr['file_size'],
+                'fv' => $file_arr['fv'],
+                'tv' => $file_arr['tv'],
                 'type' => $file_arr['type'],
                 'note' => json_encode($note, JSON_UNESCAPED_UNICODE),
                 'published_first' => $pubFirst,
@@ -90,6 +93,8 @@ class SQLiteWriter
             'file_name' => $g->filename,
             'file_size' => $g->file_size,
             'type' => $g->type,
+            'fv' => $g->fv,
+            'tv' => $g->tv,
             'note' => array(
                 'en' => $g->description_en,
                 'ja' => $g->description_ja,
@@ -98,8 +103,6 @@ class SQLiteWriter
             'pubDate' => $g->time,
         ));
         $ok = $this->insertArray('updates', array(
-            'tv' => $g->tv,
-            'fv' => $g->fv,
             'svn' => $g->svn,
             'pubDate' => $g->time,
             'publisher' => $g->publisher,
diff --git a/sql/dbschema.sql b/sql/dbschema.sql
index 7615543..ec43990 100644
--- a/sql/dbschema.sql
+++ b/sql/dbschema.sql
@@ -43,6 +43,8 @@ CREATE TABLE "files" (
   "file_name" TEXT,      -- filename of file
   "file_size" INTEGER,   -- size
   "type" TEXT,           -- FULL(4) or OTA(2) update
+  "fv" TEXT,             -- from version (only for OTA)
+  "tv" TEXT,             -- target version, e.g. AAQ302
   "note" TEXT,           -- description of file (optional)
   "published_first" INTEGER,   -- stamp of earliest pubdate
   "published_last" INTEGER     -- stamp of latest pubdate
@@ -52,18 +54,14 @@ CREATE TABLE "files" (
 -- a separate "files" table might get introduced later
 CREATE TABLE "updates" (
   "updateId" INTEGER PRIMARY KEY AUTOINCREMENT,
-  "tv" TEXT,       -- target version, e.g. AAQ302
-  "fv" TEXT,       -- from version (only for OTA)
   "svn" TEXT,      -- version info from <SVN> field
   "pubDate" INTEGER,   -- published date
   "publisher" TEXT,    -- publisher
   "fwId" TEXT,     -- <FW_ID> (CHANGES FOR THE SAME FILE_ID!!!) MAYBE MOVE TO update_map
   "file_id" TEXT,      -- <FILE_ID> of first file
-  "file_sha1" TEXT     -- SHA1 checksum of first file
+  "file_sha1" TEXT REFERENCES "files" ("sha1")     -- SHA1 checksum of first file
 );
 CREATE UNIQUE INDEX "index_updates" ON "updates" (
-  "tv",
-  "fv",
   "fwId",
   "file_id"
 );