Question

这是我的database

public void DBCreate() {
    SQLITEDATABASE = getActivity().openOrCreateDatabase("FavoritesDB", Context.MODE_PRIVATE, null);
    SQLITEDATABASE.execSQL("CREATE TABLE IF NOT EXISTS favorite(id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, word VARCHAR, meaning VARCHAR);");
}

这就是我创建新行的方式：

String query = "INSERT INTO favorite (word,meaning) VALUES('"+wordd+"', '"+mean+"');";
Cursor c=SQLITEDATABASE.rawQuery("SELECT * FROM favorite WHERE id=?", null);
if (c.moveToFirst())
{      
      Toast.makeText(getActivity(),"inserted",Toast.LENGTH_LONG).show();
                    SQLITEDATABASE.execSQL(query);
}
else
{
      Toast.makeText(getActivity(),"exists",Toast.LENGTH_LONG).show();
}

我的问题是如何在将值插入表之前检查数据？

Answer 1

在插入执行选择查询之前，检查cursor大小是否> 0比记录已存在。

我不确定您为什么在查询中传递null

 Cursor c=SQLITEDATABASE.rawQuery("SELECT * FROM favorite WHERE id=?", null);

而不是

Cursor c=SQLITEDATABASE.rawQuery("SELECT * FROM favorite WHERE id=?", new String[]{"your id1"});

或如果你想选择所有记录，那么

Cursor c=SQLITEDATABASE.rawQuery("SELECT * FROM favorite");

Answer 2

试试这段代码：

    Cursor c = SQLITEDATABASE.rawQuery("SELECT * FROM favorite WHERE id=?", new String[]{"your_id_name"});
    Log("Cursor Count : " + c.getCount());
               if(c.getCount()>0)
                {
                Toast.makeText(getActivity(),"exists",Toast.LENGTH_LONG).show();

                }
                else
                {
                   Toast.makeText(getActivity(),"inserted",Toast.LENGTH_LONG).show();
                   SQLITEDATABASE.execSQL(query);
                }

您的选择查询应如下所示：

String sql ="SELECT PID FROM "+TableName+" WHERE PID="+pidValue;

Answer 3

选项：

1）如果您不想重复列中的任何值，请将CREATE方法中的列设置设置为＆＃34; UNIQUE＆＃34;甚至＆＃34; PRIMARY KEY＆＃34;如果内容应该是识别的主键。因此，您可以避免重复，而无需检查。

2）循环通过桌子（我也是学生，所以我希望这很好）：

    Cursor c = SQLITEDATABASE.rawQuery("SELECT * FROM favorite", null);

    if (c.getCount() > 0) {

        String searchString = "some word"; // word you are about to insert

        while (c.moveToNext()) {

            c.moveToFirst();
            int colIndex = c.getColumnIndex("word");
            String wordInCurrentRow = c.getString(colIndex);

            if (!(wordInCurrentRow.equals(searchString))) {
                // insert method
            } else {
                // do nothing
                Log.d("word already existing", "nothing to insert");
            }
        }
    }

如何检查SQLite表

3 个答案: