查询空 SQLite 数据库时出错

Question

我正在编写一个 Android 应用程序，并且我有一个数据库助手 class 可以执行与 SQLite 数据库相关的任何事情。 class 的名称是 "ResultsDbAdapter"。以下是有关数据库的一些信息：

private static final String DATABASE_NAME = "PROJECT_RESULTS";
private static final String DATABASE_TABLE = "projectResults";
private static final int DATABASE_VERSION = 1;

//Fields(Columns) for Database
public static final String[] PROJECT_RESULTS_FIELDS = new String[] {
    KEY_ROWID,    
    "title",
    "interval", 
    "start",
    "end",  
    "duration",
    "totalHits",
    "itemKeys",
    "keyHits"
};

在 ResultsDbAdapter class 中是一种通过搜索 "title" 列来查询数据库中特定条目的方法。

public Cursor fetchByTitle(String pTitle) throws SQLException {
    Cursor mCursor = mDb.query(DATABASE_TABLE, PROJECT_RESULTS_FIELDS, "title" + "=" + pTitle, null,
                null, null, null, null);
    return mCursor;
}

然后在 Main Activity 中使用以下代码片段调用 "fetchByTitle" 方法：

final ResultsDbAdapter db = new ResultsDbAdapter (this);
db.open(); //Open and Close methods are also written in the "ResultsDbAdapter" class
final Cursor cursor = db.fetchByTitle(mTitle); //mTitle is the title of the record needed
if (cursor.moveToFirst()){
          // do something
 } else {
          //do something else
 }
db.close();

应用程序在模拟器上首次运行导致错误，我认为这是因为没有条目。所以没有光标到 return 导致错误。以下是来自 logcat 的错误：

03-07 21:53:51.230: E/SQLiteLog(1158): (1) near "Title": syntax error
03-07 21:53:51.310: E/AndroidRuntime(1158): FATAL EXCEPTION: main
03-07 21:53:51.310: E/AndroidRuntime(1158): Process: com.jevans.surveybud, PID: 1158
03-07 21:53:51.310: E/AndroidRuntime(1158): android.database.sqlite.SQLiteException: near "Title": syntax error (code 1): , while compiling: SELECT _id, title, interval, start, end, duration, totalHits, itemKeys, keyHits FROM projectResults WHERE title=My Title
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1161)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1032)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1238)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at com.jevans.surveybud.ResultsDbAdapter.fetchByTitle(ResultsDbAdapter.java:141)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at com.jevans.surveybud.ResultsActivity.saveDb(ResultsActivity.java:163)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at com.jevans.surveybud.ResultsActivity.onClick(ResultsActivity.java:138)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.view.View.performClick(View.java:4438)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.view.View$PerformClick.run(View.java:18422)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.os.Handler.handleCallback(Handler.java:733)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.os.Handler.dispatchMessage(Handler.java:95)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.os.Looper.loop(Looper.java:136)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at android.app.ActivityThread.main(ActivityThread.java:5017)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at java.lang.reflect.Method.invokeNative(Native Method)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at java.lang.reflect.Method.invoke(Method.java:515)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-07 21:53:51.310: E/AndroidRuntime(1158):     at dalvik.system.NativeStart.main(Native Method)

对于这个看似基本的问题，我深表歉意，因为我是 Android 编程的新手。但是，我已经坚持了很长时间。有人可以帮忙解决这个错误吗？

Answer 1

错误堆栈跟踪的这一部分表明您生成的 sql 语句 (SELECT _id, title, interval, start, end, duration, totalHits, itemKeys, keyHits FROM projectResults WHERE title=My Title) 导致 SQLiteException

03-07 21:53:51.230: E/SQLiteLog(1158): (1) near "Title": syntax error
03-07 21:53:51.310: E/AndroidRuntime(1158): FATAL EXCEPTION: main
03-07 21:53:51.310: E/AndroidRuntime(1158): Process: com.jevans.surveybud, PID: 1158
03-07 21:53:51.310: E/AndroidRuntime(1158): android.database.sqlite.SQLiteException:

要修复，请尝试利用 query() 方法参数的强大功能，使其正确绑定以进行功能性 sql 调用：

selection ("title = ?")
selectionArgs (new String[]{ pTitle})

总的来说应该是这样的：

Cursor mCursor = mDb.query(DATABASE_TABLE, 
                           PROJECT_RESULTS_FIELDS, 
                           /* selection */ "title = ?", 
                           /* selectionArgs */ new String[]{ pTitle}, 
                           null, null, null);

这应该可以解决您的 SQLiteException。

HTH

查询空 SQLite 数据库时出错

Error when query Empty SQLite DB

android

database

sqlite

cursor