Question

我是android开发的新手，我已经完成了一些教程，并使用sqlite Db编写了一个应用程序。

我有几个问题，如下所述 1.如何更新数据库中的行？ 2.删除更新的行？ 3.如何插入新行？

//下面的代码用于更新行

struct S{
        S* n
        int v;
        S(int V, S* N): n(N), v(V){};
        };

S s = S(10,new S(20,&s));
cout << (s.n->n->v);

删除特定行-下面的代码清除数据库中的全部而不是特定行

SQLiteDatabase db = dbHandler.getWritableDatabase();
for (int i = 0; i <= 100000; i = i + 100) {
    ContentValues cValues = new ContentValues();
    cValues.put(DbHandler.COLUMN_ID, i + 1);
    cValues.put(DbHandler.COLUMN_NAME, "Test");
    cValues.put(DbHandler.COLUMN_SERIALNUMBER, String.valueOf(i + 1));
    cValues.put(DbHandler.COLUMN_COUNTALL, 10);
    cValues.put(DbHandler.COLUMN_COUNTHIGH, i + 1);
    cValues.put(DbHandler.COLUMN_COUNTLOW, i + 1);
    cValues.put(DbHandler.COLUMN_RAWDATA, i + 1);
    db.update(DbHandler.TABLE_USERS, cValues, DbHandler.COLUMN_ID,new String[]{String.valueOf(i)});
}
db.close();

Answer 1

这是在SQLite中执行更新，插入和删除操作的方法

insertData

public long insertData() {
  SQLiteDatabase db = this.getWritableDatabase();
  ContentValues values = new ContentValues();

  values.put(KEY_TITLE, "Title");
  values.put(KEY_ACTIVITY_TYPE,"Event Type");
  values.put(KEY_PLACE, "Event place");
  values.put(KEY, "VALUE");
  values.put(KEY_, "VALUE");

  long id = db.insert(TABLE_NAME, null, values);
  return id;
}

updateRow

public int updateRow(String row_id) {

SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();

values.put(KEY_TITLE, "Title");
values.put(KEY_ACTIVITY_TYPE,"Event Type");
values.put(KEY_PLACE, "Event place");
values.put(KEY, "VALUE");
values.put(KEY_, "VALUE");

return db.update(TABLE_NAME, values, KEY_ID + " = ?",
        new String[]{row_id});
}

deleteRow

public int deleteRow（String row_id）{ SQLiteDatabase db = this.getWritableDatabase（）; ContentValues值=新的ContentValues（）; return db.delete（TABLE_NAME，WHERE KEY_ID +“ =？”，新的String [] {row_id}）; }

Answer 2

您可以编写dao类（数据访问对象）并使用该类这很简单，您只需在数据库上运行sql查询这个template literal将为您提供帮助

例如插入

        val query = ("insert into " + DownloaderDatabase.TABLE_NAME + " " +
            "(" +
            ColumnModel.URL + "," +
            ColumnModel.FILE_NAME + "," +
            ColumnModel.STATUS + "," +
            ColumnModel.PERCENT + "," +
            ColumnModel.SIZE + "," +
            ColumnModel.TOTAL_SIZE
            + ")" +
            " VALUES(" + "\"" + fileModel.url + "\"" + ","
            + " " + "\"" + fileModel.fileName + "\"" + ","
            + " " + fileModel.status + ","
            + " " + fileModel.percent + ","
            + " " + fileModel.size + ","
            + " " + fileModel.totalSize + ")")
    database.writableDatabase.execSQL(query)
    database.close()

例如更新

  val query = "update " + DownloaderDatabase.TABLE_NAME + " " +
            " set " + ColumnModel.STATUS + " = " + status +
            " , " + ColumnModel.PERCENT + " = " + percent +
            " , " + ColumnModel.SIZE + " = " + size +
            " , " + ColumnModel.TOTAL_SIZE + " = " + totalSize +
            " where " + ColumnModel.URL + " = " + "\"" + url + "\""
    database.writableDatabase.execSQL(query)
    database.close()

例如获取数据

        var model: FileModel? = null
    val query =
        "select * from " + DownloaderDatabase.TABLE_NAME + " where " + ColumnModel.URL + " = \"" + url + "\""
    val cursor = database.readableDatabase.rawQuery(query, null)
    while (cursor.moveToNext()) {
        val itemId = cursor.getInt(cursor.getColumnIndex(ColumnModel.ID))
        val itemUrl = cursor.getString(cursor.getColumnIndex(ColumnModel.URL))
        val itemFileName = cursor.getString(cursor.getColumnIndex(ColumnModel.FILE_NAME))
        val itemStatus = cursor.getInt(cursor.getColumnIndex(ColumnModel.STATUS))
        val itemPercent = cursor.getInt(cursor.getColumnIndex(ColumnModel.PERCENT))
        val itemSize = cursor.getInt(cursor.getColumnIndex(ColumnModel.SIZE))
        val itemTotalSize = cursor.getInt(cursor.getColumnIndex(ColumnModel.TOTAL_SIZE))
        model = FileModel(itemId, itemUrl, itemFileName, itemStatus, itemPercent, itemSize, itemTotalSize)
    }
    cursor.close()
    database.close()
    return model

Answer 3

如果要在表中插入行，请使用ContentValues（就像您的更新代码一样）和insert()方法：

SQLiteDatabase db = dbHandler.getWritableDatabase();
for (int i = 0; i < 3; i++) {
    ContentValues cValues = new ContentValues();
    cValues.put(DbHandler.COLUMN_ID, i + 1);
    cValues.put(DbHandler.COLUMN_NAME, "Test");
    cValues.put(DbHandler.COLUMN_SERIALNUMBER, String.valueOf(i + 1));
    cValues.put(DbHandler.COLUMN_COUNTALL, 10);
    cValues.put(DbHandler.COLUMN_COUNTHIGH, i + 1);
    cValues.put(DbHandler.COLUMN_COUNTLOW, i + 1);
    cValues.put(DbHandler.COLUMN_RAWDATA, i + 1);
    db.insert(DbHandler.TABLE_USERS, null, cValues);
}
db.close();

上面的代码将在表中插入3行：

1 Test 1 10 1 1 1
2 Test 2 10 2 2 2
3 Test 1 10 3 3 3

现在，假设您要用{将行的COLUMN_COUNTHIGH列更新为100，将列COLUMN_COUNTLOW更新为0 {1}}，然后使用update()方法：

id = 2

因此SQLiteDatabase db = dbHandler.getWritableDatabase(); ContentValues cValues = new ContentValues(); cValues.put(DbHandler.COLUMN_COUNTHIGH, 100); cValues.put(DbHandler.COLUMN_COUNTLOW, 0); db.update(DbHandler.TABLE_USERS, cValues, DbHandler.COLUMN_ID + " = ?", new String[] {String.valueOf(2)}); db.close();方法的参数为：
表格名称
update()
ContentValues子句，其中包含列名和占位符WHERE，这些占位符将决定要更新的行
以及将在?
处设置的列的值如果要删除，请用?说行，请使用delete()方法：

id = 1

自变量与db.delete(DbHandler.TABLE_USERS, DbHandler.COLUMN_ID + " = ?", new String[] {String.valueOf(1)});方法的自变量相似（没有ContentValues）。

如何在Sqlite中更新，插入和删除行？

3 个答案: