我正在开发一个正在开发Android移动应用程序的capstone项目。 该应用程序显示调查问题，用户让其他人回答它。答案存储在SQLite数据库表中。我成功地创建了数据库，从单选按钮获取输入，并持久地将答案存储到表中。 表中的每一列代表一个问题的答案。
现在我需要执行COUNT查询来计算每列中具有特定条件的答案数。
示例：
SELECT COUNT(KEY_GENDER)
FROM TABLE_ANSWERS
WHERE KEY_GENDER = "Female";
在上述查询中，KEY_GENDER是性别列，存储的数据是女性或男性。
TABLE_ANSWERS是表名。
该查询的功能是显示许多女性已经回答了调查。
以下是计数查询代码段，它位于数据库类中：
// count of gender.
public int countGender(){
String colName = "COUNT(" + KEY_GENDER +")" ;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT" + colName + "FROM" + TABLE_ANSWERS + "WHERE" + KEY_GENDER + "=?" + new String[] {"Female"}, null) ;
while (cursor.moveToNext()) {
int colID = cursor.getColumnIndex(KEY_GENDER);
int colID2 = cursor.getColumnIndex(colName);
}
db.close();
cursor.close();
// return count
return cursor.getCount();
}
这是另一个片段，其中查询应该使用group by显示“男性”和“女性”的数量：
// count of gender.
public int countGender(){
String colName = " COUNT(" + KEY_GENDER +") " ;
SQLiteDatabase db = this.getReadableDatabase();
// Cursor cursor = db.rawQuery("SELECT " + colName + "FROM " + TABLE_ANSWERS + " WHERE " + KEY_GENDER + "=?" + new String[] {" Female"}, null) ;
Cursor cursor = db.rawQuery("SELECT " + KEY_GENDER + colName + "FROM " + TABLE_ANSWERS + " GROUP BY " + KEY_GENDER, null) ;
while (cursor.moveToNext()) {
int colID = cursor.getColumnIndex(KEY_GENDER);
int colID2 = cursor.getColumnIndex(colName);
}
db.close();
cursor.close();
// return count
return cursor.getCount();
}
以下代码段是验证结果活动类中的onCreate方法，该方法应使用count方法查询表TABLE_ANSWERS：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_validation_results);
DatabaseHandler db = new DatabaseHandler(ValidationResults.this);
TextView gender;
gender = (TextView) findViewById(R.id.textViewGender);
int genderResult;
genderResult = db.countGender();
gender.setText(String.valueOf(genderResult));
}
catlog：
10-31 15:31:19.666 2221-2221/arwa.conceptsurvey D/dalvikvm﹕ GC_FOR_ALLOC freed 68K, 5% free 3410K/3556K, paused 13ms, total 16ms
10-31 15:31:19.754 2221-2221/arwa.conceptsurvey D/dalvikvm﹕ GC_FOR_ALLOC freed 3K, 4% free 3628K/3780K, paused 83ms, total 83ms
10-31 15:31:19.770 2221-2221/arwa.conceptsurvey I/dalvikvm-heap﹕ Grow heap (frag case) to 6.030MB for 2536932-byte allocation
10-31 15:31:19.826 2221-2230/arwa.conceptsurvey D/dalvikvm﹕ GC_FOR_ALLOC freed <1K, 3% free 6106K/6260K, paused 54ms, total 54ms
10-31 15:31:20.686 2221-2221/arwa.conceptsurvey D/libEGL﹕ loaded /system/lib/egl/libEGL_genymotion.so
10-31 15:31:20.690 2221-2221/arwa.conceptsurvey D/﹕ HostConnection::get() New Host Connection established 0xb93f2f40, tid 2221
10-31 15:31:20.774 2221-2221/arwa.conceptsurvey D/libEGL﹕ loaded /system/lib/egl/libGLESv1_CM_genymotion.so
10-31 15:31:20.774 2221-2221/arwa.conceptsurvey D/libEGL﹕ loaded /system/lib/egl/libGLESv2_genymotion.so
10-31 15:31:21.022 2221-2221/arwa.conceptsurvey W/EGL_genymotion﹕ eglSurfaceAttrib not implemented
10-31 15:31:21.022 2221-2221/arwa.conceptsurvey E/OpenGLRenderer﹕ Getting MAX_TEXTURE_SIZE from GradienCache
10-31 15:31:21.038 2221-2221/arwa.conceptsurvey E/OpenGLRenderer﹕ MAX_TEXTURE_SIZE: 16384
10-31 15:31:21.062 2221-2221/arwa.conceptsurvey E/OpenGLRenderer﹕ Getting MAX_TEXTURE_SIZE from Caches::initConstraints()
10-31 15:31:21.066 2221-2221/arwa.conceptsurvey E/OpenGLRenderer﹕ MAX_TEXTURE_SIZE: 16384
10-31 15:31:21.066 2221-2221/arwa.conceptsurvey D/OpenGLRenderer﹕ Enabling debug mode 0
10-31 15:31:21.086 2221-2221/arwa.conceptsurvey I/Choreographer﹕ Skipped 36 frames! The application may be doing too much work on its main thread.
10-31 15:32:41.710 2221-2221/arwa.conceptsurvey D/dalvikvm﹕ GC_FOR_ALLOC freed 109K, 3% free 6992K/7172K, paused 10ms, total 11ms
10-31 15:32:41.738 2221-2221/arwa.conceptsurvey E/SQLiteLog﹕ (1) near "SELECTCOUNT": syntax error
10-31 15:32:41.738 2221-2221/arwa.conceptsurvey D/AndroidRuntime﹕ Shutting down VM
10-31 15:32:41.738 2221-2221/arwa.conceptsurvey W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xa4cfab20)
10-31 15:32:41.750 2221-2221/arwa.conceptsurvey E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: arwa.conceptsurvey, PID: 2221
java.lang.RuntimeException: Unable to start activity ComponentInfo{arwa.conceptsurvey/arwa.conceptsurvey.ValidationResults}: android.database.sqlite.SQLiteException: near "SELECTCOUNT": syntax error (code 1): , while compiling: SELECTCOUNT(gender)FROMAnswers
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.database.sqlite.SQLiteException: near "SELECTCOUNT": syntax error (code 1): , while compiling: SELECTCOUNT(gender)FROMAnswers
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
at arwa.conceptsurvey.DatabaseHandler.countGender(DatabaseHandler.java:211)
at arwa.conceptsurvey.ValidationResults.onCreate(ValidationResults.java:27)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
10-31 15:32:44.474 2221-2221/arwa.conceptsurvey I/Process﹕ Sending signal. PID: 2221 SIG: 9
问题是：每当我按下导航到验证结果活动的按钮以显示查询结果时，应用程序就会停止并显示以下消息：“不幸的是，应用程序已停止”并且显然没有显示任何计数查询结果
当我从验证结果活动中取消数据库代码时，该活动当然适用于空白页面，因为它不包含任何代码。所以，我认为主要问题只来自count查询。
我从一本名为Android Database Programming的教科书中得到了这些查询的结构。 我也尝试改变结构和其他东西以使其工作。 我一直在搜索网络和教科书来解决问题，并使计数查询工作。
那么，我的计数查询有什么问题？我怎样才能使它工作并显示结果？ 我非常感谢你的帮助，因为我必须尽快提交这个项目。
提前谢谢。
更新：我在SQLite关键字之间存在语法问题。我通过在关键字中添加空格来修复上述代码。
答案 0 :(得分：6)
正如您在日志中看到的那样
"SELECTCOUNT": syntax error (code 1):
在SELECT字后添加空格：
db.rawQuery("SELECT "
同样适用于FROM和其他保留字，例如WHERE, GROUP等