android - 如何按字符串删除 sqlite 表行条目？

Question

我是 Android 的新手，我正在尝试弄清楚如何使用字符串而不是行号的 long 来删除 sqlite 中的表行。我在向表中添加数据时没有遇到任何问题，但是当我尝试删除相同的值时，出现了一个 SQL 异常，提示 SQLiteException: no such column 'my_entry': while compiling: DELETE FROM dbTABLE WHERE db_NAME = my_entry 非常感谢任何见解。这是我的代码:

添加行条目的代码:

public long createEntry(String coin, String quantity, String value) {
    ContentValues cv = new ContentValues();
    cv.put(KEY_NAME, coin);
    cv.put(KEY_QUANTITY, quantity);
    cv.put(KEY_VALUE, value);
    return ourDatabase.insert(DATABASE_TABLE, null, cv);
}

删除行条目的代码:

public void deleteEntry(String coin) throws SQLException{
    ourDatabase.delete(DATABASE_TABLE, KEY_NAME + "=" + coin, null);
}

整个数据库的代码:

public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "cointype_name";
public static final String KEY_QUANTITY = "cointype_quantity";
public static final String KEY_VALUE = "cointype_value";

private static final String DATABASE_NAME = "PortfolioDatabase";
private static final String DATABASE_TABLE = "cointypeTable";
private static final int DATABASE_VERSION = 1;

private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;

private static class DbHelper extends SQLiteOpenHelper {

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
                KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                KEY_NAME + " TEXT NOT NULL, " +
                KEY_QUANTITY  + " TEXT NOT NULL, " +
                KEY_VALUE + " TEXT NOT NULL);"
        );  
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
        onCreate(db);
    }       
}

public PortfolioDatabase(Context c){
    ourContext = c;
}

public PortfolioDatabase open() throws SQLException{
    ourHelper = new DbHelper(ourContext);
    ourDatabase = ourHelper.getWritableDatabase();
    return this;
}

 public void close(){
     ourHelper.close();
 }

public long createEntry(String coin, String quantity, String value) {
    ContentValues cv = new ContentValues();
    cv.put(KEY_NAME, coin);
    cv.put(KEY_QUANTITY, quantity);
    cv.put(KEY_VALUE, value);
    return ourDatabase.insert(DATABASE_TABLE, null, cv);
}

public String getData() {
    String[] columns = new String[]{ KEY_ROWID, KEY_NAME, KEY_QUANTITY, KEY_VALUE };
    Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
    String result = "";

    int iRow = c.getColumnIndex(KEY_ROWID);
    int iName = c.getColumnIndex(KEY_NAME);
    int iQuantity = c.getColumnIndex(KEY_QUANTITY);
    int iValue = c.getColumnIndex(KEY_VALUE);

    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
        result = result + c.getString(iRow) + " " + c.getString(iName) + " " + c.getString(iQuantity) + " " + c.getString(iValue) + "\n";
    }

    return result;
}

public String getName(long l) throws SQLException{
    String[] columns = new String[]{ KEY_ROWID, KEY_NAME, KEY_QUANTITY, KEY_VALUE};
    Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + l, null, null, null, null);
    if (c != null){
        c.moveToFirst();
        String name = c.getString(1);
        return name;
    }
    return null;
}

public String getHotness(long l) throws SQLException{
    String[] columns = new String[]{ KEY_ROWID, KEY_NAME, KEY_QUANTITY, KEY_VALUE };
    Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + l, null, null, null, null);
    if (c != null){
        c.moveToFirst();
        String hotness = c.getString(2);
        return hotness;
    }
    return null;
}

public void updateEntry(String mCoin, String mQuantity, String mValue) throws SQLException {
    ContentValues cvUpdate = new ContentValues();
    cvUpdate.put(KEY_NAME, mCoin);
    cvUpdate.put(KEY_QUANTITY, mQuantity);
    cvUpdate.put(KEY_VALUE, mValue);
    ourDatabase.update(DATABASE_TABLE, cvUpdate, KEY_NAME + "=" + mCoin, null); 
}

public void deleteEntry(String coin) throws SQLException {
    ourDatabase.delete(DATABASE_TABLE, KEY_NAME + "=" + coin, null);
}
}

Answer 1

您不应该直接使用该字符串，如果您需要将其包装在 ' 中，否则 SQLite 会将其视为列名。

最安全的方法是

public void deleteEntry(String coin) throws SQLException{
    String[] whereArgs = new String[] { coin };
    ourDatabase.delete(DATABASE_TABLE, KEYNAME + "=?", whereArgs);
}

不安全的方式是

ourDatabase.delete(DATABASE_TABLE, KEYNAME + "='" + coin + "'", null);

如果 coin 包含 '，那将失败，所以不要使用它。