Question

所以我在我的DBAdapter类中遇到问题，当我尝试打开数据库时它只会崩溃：来自LogCat，我猜问题出现在onUpgrade函数中：

 public void onUpgrade(SQLiteDatabase db, int oldVersion,
 int newVersion)
  {
       Log.w("SingleDBAdapter", "Upgrading database from version " + oldVersion
       + " to "
       + newVersion + ", which will destroy all old data");
       db.execSQL("DROP TABLE IF EXISTS "+DATABASE_TABLE);
       onCreate(db);
  }
 }

这是错误：

07-28 11:32:49.443: E/Database(1244): Failure 1 (near "122": syntax error) on 0x2435b0 when preparing 'DROP TABLE IF EXISTS 122'.
07-28 11:32:49.463: D/AndroidRuntime(1244): Shutting down VM
07-28 11:32:49.463: W/dalvikvm(1244): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
07-28 11:32:49.473: E/AndroidRuntime(1244): FATAL EXCEPTION: main
07-28 11:32:49.473: E/AndroidRuntime(1244): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.shop.list/com.shop.list.main}: android.database.sqlite.SQLiteException: near "122": syntax error: **DROP TABLE IF EXISTS 122**
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.os.Looper.loop(Looper.java:123)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.ActivityThread.main(ActivityThread.java:4627)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at java.lang.reflect.Method.invokeNative(Native Method)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at java.lang.reflect.Method.invoke(Method.java:521)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at dalvik.system.NativeStart.main(Native Method)
07-28 11:32:49.473: E/AndroidRuntime(1244): Caused by: android.database.sqlite.SQLiteException: near "122": syntax error: DROP TABLE IF EXISTS 122
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.database.sqlite.SQLiteDatabase.native_execSQL(Native Method)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1727)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at com.shop.list.ListDBAdapter$DatabaseHelper.onUpgrade(ListDBAdapter.java:51)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:108)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at com.shop.list.ListDBAdapter.open(ListDBAdapter.java:60)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at com.shop.list.main.onCreate(main.java:60)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-28 11:32:49.473: E/AndroidRuntime(1244):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
07-28 11:32:49.473: E/AndroidRuntime(1244):     ... 11 more

我突出了问题，但我无法解决它：/

Answer 1

问题似乎在于这句话：

DROP TABLE IF EXISTS 122

其中122，如果它实际上是要删除的表的名称，则不会分隔（例如，使用'），因此不能将其视为名称。但是解析器需要一个名字。只需将名称括在单引号或双引号中，它就应该起作用：

db.execSQL("DROP TABLE IF EXISTS '" + DATABASE_TABLE + "'");

Answer 2

如果表名都是字母字符，那么原始代码就可以了。由于表名不是全部字母，因此需要用单引号括起来。

Answer 3

我认为你错过了一个＆＃39 ;;＆＃39;在SQL语句的末尾

除此之外，我刚刚检查了一个sqlite3控制台，似乎＆＃34; 122＆＃34;是一个无效的表名：

sqlite> drop table if exists 122;
Error: near "122": syntax error
sqlite> drop table if exists test;
sqlite>

Answer 4

db =这是您的数据库处理程序类

db.execSQL("DROP TABLE IF EXISTS YourTableName");

Answer 5

您好，您应该使用致电声明： “context.deleteDatabase（DATABASE_NAME）;”

在调用“onCreate（）;”之前

public void onUpgrade(SQLiteDatabase db, int oldVersion,
 int newVersion)
  {
       Log.w("SingleDBAdapter", "Upgrading database from version " + oldVersion
       + " to "
       + newVersion + ", which will destroy all old data");
       context.deleteDatabase(DATABASE_NAME);
       onCreate(db);
  }
 }

Answer 6

你应该改变你的：

db.execSQL("DROP TABLE IF EXISTS "+DATABASE_TABLE);

使用：

db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE + ";");

另外，您需要检查newVersion＆gt; oldVersion

sqlite中的错误＆＃34; DROP TABLE IF EXISTS＆＃34;安卓

6 个答案: