Android 如何在sqlite的原始查询中使用交叉连接_Android_Sqlite

Android 如何在sqlite的原始查询中使用交叉连接

android sqlite

Android 如何在sqlite的原始查询中使用交叉连接,android,sqlite,Android,Sqlite,我在谷歌上搜索过，发现我也可以在SQlite Android中进行交叉连接，我尝试过，但结果是空的。我的程序有问题吗？或者实际上不能在原始查询中应用交叉联接？谢谢你的帮助注意：在使用交叉联接之前，我尝试发送一个表（以JSONArray形式），并且它正在工作，所以我假设在代码中使用交叉联接时会发生这种情况以下是我的节目： private JSONArray getResults() { Context context = this; String myPath = Strin

我在谷歌上搜索过，发现我也可以在SQlite Android中进行交叉连接，我尝试过，但结果是空的。我的程序有问题吗？或者实际上不能在原始查询中应用交叉联接？谢谢你的帮助

注意：在使用交叉联接之前，我尝试发送一个表（以JSONArray形式），并且它正在工作，所以我假设在代码中使用交叉联接时会发生这种情况

以下是我的节目：

private JSONArray getResults()
{
    Context context = this;

    String myPath = String.valueOf(context.getDatabasePath("ekantin1.db"));// Set path to your database

    //String myTable = DatabaseHelper.ORDER_TABLE_NAME;//Set name of your table

    SQLiteDatabase myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    //String searchQuery = "SELECT  * FROM " + myTable;
    Cursor cursor = myDataBase.rawQuery(" SELECT * FROM " + DatabaseHelper.ORDER_TABLE_NAME + " CROSS JOIN " + DatabaseHelper.LINEITEMS_TABLE_NAME, null );

    JSONArray resultSet     = new JSONArray();

    cursor.moveToFirst();
    while (cursor.isAfterLast() == false) {

        int totalColumn = cursor.getColumnCount();
        JSONObject rowObject = new JSONObject();

        for( int i=0 ;  i< totalColumn ; i++ )
        {
            if( cursor.getColumnName(i) != null )
            {
                try
                {
                    if( cursor.getString(i) != null )
                    {
                        Log.d("TAG_NAME", cursor.getString(i) );
                        rowObject.put(cursor.getColumnName(i) ,  cursor.getString(i) );
                    }
                    else
                    {
                        rowObject.put( cursor.getColumnName(i) ,  "" );
                    }
                }
                catch( Exception e )
                {
                    Log.d("TAG_NAME", e.getMessage()  );
                }
            }
        }
        resultSet.put(rowObject);
        cursor.moveToNext();
    }
    cursor.close();
    Log.d("TAG_NAME", resultSet.toString() );


    Intent pass_data = new Intent(this,BluetoothOut.class);

    pass_data.putExtra("pindah",resultSet.toString());
    startActivity(pass_data);

    return resultSet;
}
}

我的程序有问题吗

仅仅看一眼就看不出来

或者实际上不能在原始查询中应用交叉联接

我认为没有这样的限制

我认为问题在于tb\u lineitems表中没有行。因此，

SELECT*FROM tb_order

将返回行。但是，当您加入tb_lineitems表时，不会返回任何已加入的行

例如，使用（注意注释SQL时如何不插入任何行项目）：-

结果如下3个输出：-

从3个tb_行项目的插入中删除注释，结果如下：-

请注意，交叉联接的结果与联接的结果没有什么不同，如下所示：-
如果联接运算符为“交叉联接”、“内部联接”、“联接”或逗号（“，”）并且没有ON或USING子句，则连接的结果只是左右手数据集的笛卡尔乘积

再次评论：-

我已经检查了数据库，tb_行项目和tb_顺序不正确空的

您检查了哪个数据库？根据对代码的仔细检查，您正在尝试使用2。

在数据库帮助程序中，您已将数据库定义为ekantins.db。但是，您可以在

getResults

方法中打开名为ekanti1.db的数据库

在下文中，请注意以下代码：-

    //String myPath = String.valueOf(context.getDatabasePath("ekantin1.db"));// Set path to your database
    String myPath = String.valueOf(context.getDatabasePath("ekantins.db"));// Set path to your database

运行对代码的轻微修改，并且仅使用1个数据库

添加到数据库帮助器的两个方法，用于添加订单和行项目（不包括）
以下代码被用作活动（即您的代码+多一点）
- 尝试启动另一个活动已被注释掉
- ```
getResults
```
  方法被调用两次，即在有任何数据之前和之后

：-

public类MainActivity扩展了AppCompatActivity{
数据库助手mDBHlpr；
光标；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
mDBHlpr=新数据库助手（此）；
JSONArray r1=getResults（）；
String sql=“SELECT*FROM”+DatabaseHelper.ORDER\u TABLE\u NAME+“交叉连接”+DatabaseHelper.LINEITEMS\u TABLE\u NAME；
cursor=mDBHlpr.getWritableDatabase（）.rawQuery（sql，null）；
DatabaseUtils.dumpCursor（cursor）；
//只添加一次数据
if（DatabaseUtils.queryNumEntries（mDBHlpr.getwriteabledatabase（），DatabaseHelper.ORDER\u TABLE\u NAME）<1）{
mDBHlpr.addOrder（“Fred”、“密码”、“m001”、“t001”、“s001”）；
mDBHlpr.addOrder（“玛丽”、“密码”、“m001”、“t001”、“s001”）；
mDBHlpr.addOrder（“Bert”、“密码”、“m001”、“t001”、“s001”）；
cursor=mDBHlpr.getWritableDatabase（）.rawQuery（sql，null）；
DatabaseUtils.dumpCursor（cursor）；
mDBHlpr.addLineItem（“F001”、“10.30”、“1”、“1”和“1”）；
mDBHlpr.addLineItem（“F002”、“11.30”、“2”、“2”和“1”）；
mDBHlpr.addLineItem（“F003”、“12.30”、“3”、“3”和“2”）；
cursor=mDBHlpr.getWritableDatabase（）.rawQuery（sql，null）；
DatabaseUtils.dumpCursor（cursor）；
}
JSONArray r2=getResults（）；
}
私有JSONArray getResults（）
{
上下文=这个；
//String myPath=String.valueOf（context.getDatabasePath（“ekanti1.db”）；//设置数据库的路径
String myPath=String.valueOf（context.getDatabasePath（“ekantis.db”）；//设置数据库的路径
String myTable=DatabaseHelper.ORDER\u TABLE\u NAME；//设置表的名称
SQLiteDatabase myDataBase=SQLiteDatabase.openDatabase（myPath，null，SQLiteDatabase.OPEN\u READONLY）；
//SQLiteDatabase myDataBase=mDBHlpr.getWritableDatabase（）；
//String searchQuery=“SELECT*FROM”+myTable；
Cursor Cursor=myDataBase.rawQuery（“选择*自”+DatabaseHelper.ORDER\u TABLE\u NAME+“交叉连接”+DatabaseHelper.LINEITEMS\u TABLE\u NAME，null）；
JSONArray resultSet=新的JSONArray（）；
cursor.moveToFirst（）；
while（cursor.isAfterLast（）==false）{
int totalColumn=cursor.getColumnCount（）；
JSONObject rowObject=新的JSONObject（）；
对于（int i=0；iDROP TABLE IF EXISTS tb_order;
CREATE TABLE IF NOT EXISTS tb_order (ORDERID  INTEGER PRIMARY KEY AUTOINCREMENT,USERID TEXT ,PASSWORD TEXT, MEJA TEXT, TOPUP TEXT, SALDO TEXT);
DROP TABLE IF EXISTS tb_lineitems;
CREATE TABLE IF NOT EXISTS tb_lineitems (FOODID TEXT ,PRICE TEXT, NUM TEXT, RES TEXT, ORDERID_FK INTEGER);
INSERT INTO tb_order VALUES
    (null,'Fred','password','meja001','topup001','saldo001'),
    (null,'Mary','password','meja002','topup002','saldo002'),
    (null,'Bert','password','meja003','topup003','saldo003');
/*
INSERT INTO tb_lineitems VALUES
    ('food001','10.30','1','res001',1),
    ('food002','11.30','1','res002',1),
    ('food002','11.30','1','res002',2)
    ;
*/
SELECT * FROM tb_order;
SELECT * FROM tb_lineitems;
SELECT * FROM tb_order 
      CROSS 
JOIN tb_lineitems 
;


    //String myPath = String.valueOf(context.getDatabasePath("ekantin1.db"));// Set path to your database
    String myPath = String.valueOf(context.getDatabasePath("ekantins.db"));// Set path to your database

public class MainActivity extends AppCompatActivity {

    DatabaseHelper mDBHlpr;
    Cursor cursor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        mDBHlpr = new DatabaseHelper(this);
        JSONArray r1 = getResults();

        String sql = " SELECT * FROM " + DatabaseHelper.ORDER_TABLE_NAME + " CROSS JOIN " + DatabaseHelper.LINEITEMS_TABLE_NAME;


        cursor = mDBHlpr.getWritableDatabase().rawQuery(sql, null );
        DatabaseUtils.dumpCursor(cursor);

        // Only add data once
        if (DatabaseUtils.queryNumEntries(mDBHlpr.getWritableDatabase(),DatabaseHelper.ORDER_TABLE_NAME) < 1) {

            mDBHlpr.addOrder("Fred", "password", "m001", "t001", "s001");
            mDBHlpr.addOrder("Mary", "password", "m001", "t001", "s001");
            mDBHlpr.addOrder("Bert", "password", "m001", "t001", "s001");

            cursor = mDBHlpr.getWritableDatabase().rawQuery(sql, null);
            DatabaseUtils.dumpCursor(cursor);

            mDBHlpr.addLineItem("F001", "10.30", "1", "1", 1);
            mDBHlpr.addLineItem("F002", "11.30", "2", "2", 1);
            mDBHlpr.addLineItem("F003", "12.30", "3", "3", 2);

            cursor = mDBHlpr.getWritableDatabase().rawQuery(sql, null);
            DatabaseUtils.dumpCursor(cursor);
        }

        JSONArray r2 = getResults();
    }

    private JSONArray getResults()
    {
        Context context = this;

        //String myPath = String.valueOf(context.getDatabasePath("ekantin1.db"));// Set path to your database

        String myPath = String.valueOf(context.getDatabasePath("ekantins.db"));// Set path to your database

        String myTable = DatabaseHelper.ORDER_TABLE_NAME;//Set name of your table

        SQLiteDatabase myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
        //SQLiteDatabase myDataBase = mDBHlpr.getWritableDatabase();
        //String searchQuery = "SELECT  * FROM " + myTable;
        Cursor cursor = myDataBase.rawQuery(" SELECT * FROM " + DatabaseHelper.ORDER_TABLE_NAME + " CROSS JOIN " + DatabaseHelper.LINEITEMS_TABLE_NAME, null );

        JSONArray resultSet     = new JSONArray();

        cursor.moveToFirst();
        while (cursor.isAfterLast() == false) {

            int totalColumn = cursor.getColumnCount();
            JSONObject rowObject = new JSONObject();

            for( int i=0 ;  i< totalColumn ; i++ )
            {
                if( cursor.getColumnName(i) != null )
                {
                    try
                    {
                        if( cursor.getString(i) != null )
                        {
                            Log.d("TAG_NAME", cursor.getString(i) );
                            rowObject.put(cursor.getColumnName(i) ,  cursor.getString(i) );
                        }
                        else
                        {
                            rowObject.put( cursor.getColumnName(i) ,  "" );
                        }
                    }
                    catch( Exception e )
                    {
                        Log.d("TAG_NAME", e.getMessage()  );
                    }
                }
            }
            resultSet.put(rowObject);
            cursor.moveToNext();
        }
        cursor.close();
        Log.d("TAG_NAME", resultSet.toString() );


        /*
        Intent pass_data = new Intent(this,BluetoothOut.class);

        pass_data.putExtra("pindah",resultSet.toString());
        startActivity(pass_data);
        */

        return resultSet;
    }
}

08-04 07:05:36.895 1494-1494/pra.playrawaudio D/TAG_NAME: []
08-04 07:05:36.895 1494-1494/pra.playrawaudio I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@5343e554
    <<<<<
08-04 07:05:36.907 1494-1494/pra.playrawaudio I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@53441ce0
    <<<<<
08-04 07:05:36.915 1494-1494/pra.playrawaudio I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@53437acc
    0 {
       ORDERID=1
       USERID=Fred
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F001
       PRICE=10.30
       NUM=1
       RES=1
       ORDERID_FK=1
    }
    1 {
       ORDERID=1
       USERID=Fred
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F002
       PRICE=11.30
       NUM=2
       RES=2
       ORDERID_FK=1
    }
    2 {
       ORDERID=1
       USERID=Fred
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F003
       PRICE=12.30
       NUM=3
       RES=3
       ORDERID_FK=2
    }
    3 {
       ORDERID=2
       USERID=Mary
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F001
       PRICE=10.30
       NUM=1
       RES=1
       ORDERID_FK=1
    }
    4 {
       ORDERID=2
       USERID=Mary
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F002
       PRICE=11.30
       NUM=2
       RES=2
       ORDERID_FK=1
    }
    5 {
       ORDERID=2
       USERID=Mary
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F003
       PRICE=12.30
       NUM=3
       RES=3
       ORDERID_FK=2
    }
    6 {
       ORDERID=3
       USERID=Bert
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F001
       PRICE=10.30
       NUM=1
       RES=1
       ORDERID_FK=1
    }
    7 {
       ORDERID=3
       USERID=Bert
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F002
       PRICE=11.30
       NUM=2
       RES=2
       ORDERID_FK=1
    }
    8 {
       ORDERID=3
       USERID=Bert
       PASSWORD=password
       MEJA=m001
       TOPUP=t001
       SALDO=s001
       FOODID=F003
       PRICE=12.30
       NUM=3
       RES=3
       ORDERID_FK=2
    }
    <<<<<
08-04 07:05:36.919 1494-1494/pra.playrawaudio D/TAG_NAME: 1
    Fred
    password
    m001
    t001
    s001
    F001
    10.30
    1
    1
    1
08-04 07:05:36.923 1494-1494/pra.playrawaudio D/TAG_NAME: 1
    Fred
    password
    m001
    t001
    s001
    F002
    11.30
    2
    2
    1
    1
    Fred
    password
    m001
    t001
    s001
    F003
    12.30
    3
    3
    2
    2
    Mary
    password
    m001
    t001
    s001
    F001
    10.30
    1
    1
    1
    2
    Mary
    password
    m001
    t001
    s001
    F002
    11.30
    2
    2
    1
    2
    Mary
    password
    m001
    t001
    s001
    F003
    12.30
    3
    3
    2
    3
    Bert
    password
    m001
    t001
    s001
    F001
    10.30
    1
    1
    1
    3
    Bert
    password
    m001
    t001
    s001
    F002
    11.30
    2
    2
    1
    3
    Bert
    password
    m001
    t001
    s001
    F003
    12.30
    3
    3
    2
08-04 07:05:36.927 1494-1494/pra.playrawaudio D/TAG_NAME: [{"PRICE":"10.30","RES":"1","ORDERID":"1","SALDO":"s001","MEJA":"m001","ORDERID_FK":"1","PASSWORD":"password","NUM":"1","TOPUP":"t001","FOODID":"F001","USERID":"Fred"},{"PRICE":"11.30","RES":"2","ORDERID":"1","SALDO":"s001","MEJA":"m001","ORDERID_FK":"1","PASSWORD":"password","NUM":"2","TOPUP":"t001","FOODID":"F002","USERID":"Fred"},{"PRICE":"12.30","RES":"3","ORDERID":"1","SALDO":"s001","MEJA":"m001","ORDERID_FK":"2","PASSWORD":"password","NUM":"3","TOPUP":"t001","FOODID":"F003","USERID":"Fred"},{"PRICE":"10.30","RES":"1","ORDERID":"2","SALDO":"s001","MEJA":"m001","ORDERID_FK":"1","PASSWORD":"password","NUM":"1","TOPUP":"t001","FOODID":"F001","USERID":"Mary"},{"PRICE":"11.30","RES":"2","ORDERID":"2","SALDO":"s001","MEJA":"m001","ORDERID_FK":"1","PASSWORD":"password","NUM":"2","TOPUP":"t001","FOODID":"F002","USERID":"Mary"},{"PRICE":"12.30","RES":"3","ORDERID":"2","SALDO":"s001","MEJA":"m001","ORDERID_FK":"2","PASSWORD":"password","NUM":"3","TOPUP":"t001","FOODID":"F003","USERID":"Mary"},{"PRICE":"10.30","RES":"1","ORDERID":"3","SALDO":"s001","MEJA":"m001","ORDERID_FK":"1","PASSWORD":"password","NUM":"1","TOPUP":"t001","FOODID":"F001","USERID":"Bert"},{"PRICE":"11.30","RES":"2","ORDERID":"3","SALDO":"s001","MEJA":"m001","ORDERID_FK":"1","PASSWORD":"password","NUM":"2","TOPUP":"t001","FOODID":"F002","USERID":"Bert"},{"PRICE":"12.30","RES":"3","ORDERID":"3","SALDO":"s001","MEJA":"m001","ORDERID_FK":"2","PASSWORD":"password","NUM":"3","TOPUP":"t001","FOODID":"F003","USERID":"Bert"}]
08-04 07:05:36.951 1494-1494/pra.playrawaudio I/dalvikvm: Could not find method android.view.ViewGroup$MarginLayoutParams.getLayoutDirection, referenced from method android.support.v4.view.MarginLayoutParamsCompat.getLayoutDirection