Question

我有一个数据库应用程序。最初我想把个人的细节。后来我想展示他们的形象。这是我的SQLiteOpenHeloer类---

public class FriendsDbHelper extends SQLiteOpenHelper {

    public FriendsDbHelper(Context context) {
        super(context, TABLE_NAME, null, FriendContract.FriendEntry.DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        updateData(db,0,FriendContract.FriendEntry.DATABASE_VERSION);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        updateData(db,oldVersion,newVersion);
    }

    private void updateData(SQLiteDatabase db,int oldVersion,int newVersion)
    {
        if(oldVersion<1)
        {
            String SQL_CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + " ("
                    + FriendContract.FriendEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
                    + FriendContract.FriendEntry.NAME + " TEXT NOT NULL,"
                    + FriendContract.FriendEntry.DESCRIPTION + " TEXT,"
                    + FriendContract.FriendEntry.RESIDENCE + " TEXT,"
                    + FriendContract.FriendEntry.STATUS + " TEXT );";    
            db.execSQL(SQL_CREATE_TABLE);
        }    
        if(oldVersion<2)
        {
            String SQL_CREATE_TABLE="ALTER TABLE "+TABLE_NAME+ "ADD COLUMN "+ KEY_IMAGE +"BLOB";
            db.execSQL(SQL_CREATE_TABLE);
        }    
    }
}

这是FriendContract类---

public  class FriendContract {

    private FriendContract()
    {    
    }

    public static final class FriendEntry implements BaseColumns {

        public static final int DATABASE_VERSION = 2;    
        public static final String TABLE_NAME = "friends";   
        public static final String _ID = BaseColumns._ID;    
        public static final String NAME = "name";    
        public static final String DESCRIPTION = "description";    
        public static final String RESIDENCE = "residence";    
        public static final String STATUS = "status";    
        public static final String KEY_IMAGE="image_data";    
    }
}

显示错误-----

SQLiteException：没有这样的列：image_data（代码1）:,同时编译：SELECT _id，image_data，name，description，residence，status FROM friends

它将错误指向主要活动中的以下行---

Cursor newCursor=db.query(TABLE_NAME,new String[]{_ID,NAME,DESCRIPTION,RESIDENCE,STATUS,KEY_IMAGE},null,null,null,n ULL，NULL）;

错误是什么？请解释一下。

Answer 1

问题在于： -

String SQL_CREATE_TABLE="ALTER TABLE "+TABLE_NAME+ "ADD COLUMN "+ KEY_IMAGE +"BLOB";

这解析为ALTER TABLE friendsADD COLUMN image_dataBLOB

表名和ADD之间以及列名和列类之间需要一个空格，即它应该是： -

String SQL_CREATE_TABLE="ALTER TABLE "+TABLE_NAME+ " ADD COLUMN "+ KEY_IMAGE +" BLOB"; //<<<< space added before BLOB

SQLiteException：没有这样的列：image_data（代码1）:,同时编译：SELECT _id，image_data，name，description，residence，status FROM friends

1 个答案: