Question

所以我使用SQLite为我的Android应用程序创建数据库，出于某种原因，它认为我的专栏＆＃34; START_DATE_COLUMN＆＃34;不存在（我的日志语句为列索引返回-1）。这很奇怪，因为当我在SQLite浏览器中查看.db文件时，列中包含我添加的所有条目。

这是我的DatabaseHelper类的代码：

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.BaseColumns;
import android.util.Log;

public class DatabaseHelper extends SQLiteOpenHelper implements BaseColumns {

public static final int DATABASE_VERSION = 3;
public static final String DATABASE_NAME = "JobEntries.db";
public static final String TABLE_NAME = "jobs";
public static final String NAME_COLUMN = "name";
public static final String START_DATE_COLUMN = "startDate";

private static final String SQL_CREATE_ENTRIES = "CREATE TABLE " + TABLE_NAME + " " +
        "(" + _ID + " INTEGER PRIMARY KEY, "
        + NAME_COLUMN
        + " TEXT, "
        + START_DATE_COLUMN
        + " TEXT)";
private static final String SQL_DELETE_ENTRIES = "DROP TABLE IF EXISTS " + TABLE_NAME;

public DatabaseHelper(Context context){
   super(context,DATABASE_NAME,null,DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(SQL_CREATE_ENTRIES);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL(SQL_DELETE_ENTRIES);
    onCreate(db);
}

public boolean insertJob(JobEntry job){
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(this.NAME_COLUMN, job.getClientName());
    contentValues.put(this.START_DATE_COLUMN, job.getStartDate());
    db.insert(this.TABLE_NAME,null,contentValues);
    return true;
}

public Cursor getDataByDate(String startDate){
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor result = db.rawQuery("SELECT " + NAME_COLUMN + " FROM " +TABLE_NAME+" WHERE " +START_DATE_COLUMN+ " =" +startDate+"",null);
    result.moveToFirst();
    Log.d("Column Index ", Integer.toString(result.getColumnIndex(START_DATE_COLUMN)));
    return result;
}
}

Answer 1

startDate是一个文本

尝试在您的查询whereArgs中添加单引号＆＃39; ，并将START_DATE_COLUMN添加到您选择的列中，如：

Cursor result = db.rawQuery("SELECT " + NAME_COLUMN + ", " + START_DATE_COLUMN + " FROM " +TABLE_NAME+" WHERE " +START_DATE_COLUMN+ " = '" +startDate+ "' ",null);

或

Cursor result = db.query(TABLE_NAME, new String[] { NAME_COLUMN, START_DATE_COLUMN }, START_DATE_COLUMN + " = ? ", new String[] { startDate }, null, null, null );

Answer 2

这是您引用的日志语句吗？

Log.d("Column Index ", Integer.toString(result.getColumnIndex(START_DATE_COLUMN)));

如果是这样，它返回-1，因为您没有在先前在方法中构建的SELECT语句中选择START_DATE_COLUMN。这将是修改SELECT语句以包含该列的一种方法：

Cursor result = db.rawQuery("SELECT " + NAME_COLUMN + ", " + START_DATE_COLUMN + " FROM " +TABLE_NAME+" WHERE " +START_DATE_COLUMN+ " =" +startDate+"",null);

Answer 3

这个db.rawQuery("SELECT " + NAME_COLUMN + " FROM " +TABLE_NAME+" WHERE " +START_DATE_COLUMN+ " =" +startDate+"",null);会产生这样的结果。你得到-1，因为你只查询来自NAME_COLUMN的数据，

+-------------------+
|       name        |
+-------------------+
| Android Developer |
| Python Developer  |
| Django Developer  |
+-------------------+

如果您还想包含START_DATE_COLUMN，那么我们可以将查询更改为"SELECT * FROM " +TABLE_NAME+" WHERE " + START_DATE_COLUMN + " =" +startDate+""或"SELECT " + NAME_COLUMN + ", " + START_DATE_COLUMN + " FROM " +TABLE_NAME+" WHERE " +START_DATE_COLUMN+ " =" +startDate+""，这将产生：

+-------------------+--------------+
|       Name        |  startDate   |
+-------------------+--------------+
| Android Developer | October 16th |
| Python Developer  | October 17th |
| Django Developer  | October 18th |
+-------------------+--------------+

现在，Integer.toString(result.getColumnIndex(START_DATE_COLUMN))不会返回-1。

Android SQLiteDatabase列不存在

3 个答案: