diff --git a/app/src/main/java/io/legado/app/data/entities/Chapter.kt b/app/src/main/java/io/legado/app/data/entities/Chapter.kt
index f69bb4ac0..fa359a582 100644
--- a/app/src/main/java/io/legado/app/data/entities/Chapter.kt
+++ b/app/src/main/java/io/legado/app/data/entities/Chapter.kt
@@ -10,14 +10,19 @@ import kotlinx.android.parcel.Parcelize
 
 @Parcelize
 @Entity(tableName = "chapters",
-    indices = [(Index(value = ["feedId", "feedLink"], unique = true))])
+    indices = [(Index(value = ["url"], unique = true)), (Index(value = ["bookUrl", "index"], unique = true))],
+    foreignKeys = [(ForeignKey(entity = Book::class,
+        parentColumns = ["descUrl"],
+        childColumns = ["bookUrl"],
+        onDelete = ForeignKey.CASCADE))])    // 删除书籍时自动删除章节
 data class Chapter(@PrimaryKey
-                    var name: String = "",
-                    var bookUrl: String = "",
-                    var index: Int = 0,
-                    var resourceUrl: String? = null,
-                    var tag: String? = null,
-                    var start: Long? = null,
-                    var end: Long? = null
+                    var url: String = "",               // 章节地址
+                    var name: String = "",              // 章节标题
+                    var bookUrl: String = "",           // 书籍地址
+                    var index: Int = 0,                 // 章节序号
+                    var resourceUrl: String? = null,    // 音频真实URL
+                    var tag: String? = null,            //
+                    var start: Long? = null,            // 章节起始地址
+                    var end: Long? = null               // 章节终止地址
 ) : Parcelable