我有一个这样的桌子
registrationId | standardId | courseId | marks
===============================================
5001 | 1 | 1 | 67
5001 | 1 | 2 | 87
等等，我的问题是标准名称和课程名称来自不同的表，因此在更新时，我必须使用3个不同的查询，首先根据课程名称的标准名称Courseid获取standardId，然后再更新到该表中。可以在一个查询中完成吗？
答案 0 :(得分：0)
标点符号存在是有原因的；您应该使用它。没有它，那么长的句子很难阅读和理解。
标题说“插入”，正文说“更新”；哪一个？
对于public class MainActivity extends AppCompatActivity
{
private static final String TAG = "MainActivity";
EditText cityName;
String city = null;
ListView dayListView;
ArrayList<WeatherData> weatherDataArrayList;
DayAdapter dayAdapter;
//private String responseJSON = null;
//WeatherAdapter weatherAdapter = null; // Creating this adapter within the DayAdapter
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cityName = (EditText) findViewById(R.id.cityName);
Button load = (Button) findViewById(R.id.loadButton);
dayListView = (ListView) findViewById(R.id.dayList);
load.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
city = cityName.getText().toString();
Log.d(TAG, "onClick: city is : " + city);
if (city == null)
{
Toast toast = null;
toast.makeText(MainActivity.this,"Please Enter a city before continuing",Toast.LENGTH_LONG);
toast.show();
}
else
{
String url = "http://api.openweathermap.org/data/2.5/forecast?q=" + (city.toLowerCase()) + "&units=metric&appid=8b10912e19fde267f36f6cb785ee7efd";
Log.d(TAG, "onCreate: staring download task");
DownloadJSON downloadJSON = new DownloadJSON();
downloadJSON.execute(url);
Log.d(TAG, "onCreate: after downloadtask");
}
}
});
}
public void SetDayListData(ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock)
{
if (dayAdapter == null)
{
dayAdapter = new DayAdapter(MainActivity.this,R.layout.layout_day_card, days, weatherDataArrayList);
dayListView.setAdapter(dayAdapter);
}
else
{
//created a new method "UpdateData" just to update the data in the adapter
dayAdapter.UpdateData(days, weatherDataArrayList);
dayAdapter.notifyDataSetChanged();
}
}
private class DownloadJSON extends AsyncTask<String, Void, String>
{
private static final String TAG = "DownloadJSON";
private String downloadJSON(String url)
{
StringBuilder jsonResult = new StringBuilder();
try
{
URL apiURL = new URL(url);
HttpURLConnection connection = (HttpURLConnection) apiURL.openConnection();
int responseCode = connection.getResponseCode();
Log.d(TAG, "downloadJSON: Response code "+ responseCode);
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
int charReader;
char[] inputBuffer = new char[500];
while (true)
{
charReader = reader.read(inputBuffer);
if (charReader < 0)
{
break;
}
if (charReader > 0)
{
jsonResult.append(String.copyValueOf(inputBuffer, 0, charReader));
}
}
reader.close();
return jsonResult.toString();
}
catch (MalformedURLException e)
{
Log.e(TAG, "downloadJSON: URL is Invalid");
}
catch (IOException e)
{
Log.e(TAG, "downloadJSON: IO Error");
}
return null;
}
@Override
protected String doInBackground(String... strings)
{
Log.d(TAG, "doInBackground: url is : " + strings[0]);
String jsonResponse = downloadJSON(strings[0]);
if (jsonResponse == null)
{
Log.e(TAG, "doInBackground: Error downloading");
}
return jsonResponse;
}
@Override
protected void onPostExecute(String jsonResponse)
{
super.onPostExecute(jsonResponse);
Log.d(TAG, "onPostExecute: json received is : " + jsonResponse);
if (jsonResponse != null)
{
JsonToWeatherData jtwd = new JsonToWeatherData();
weatherDataArrayList = jtwd.extractor(jsonResponse);
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
String date1 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date2 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date3 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date4 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date5 = simpleDateFormat.format(calendar.getTime());
ArrayList<String> days = new ArrayList<>();
days.add(date1);
days.add(date2);
days.add(date3);
days.add(date4);
days.add(date5);
SetDayListData(days, weatherDataArrayList);
}
else
{
Log.d(TAG, "onPostExecute: no json recieved, city is Wrong");
Toast toast = Toast.makeText(MainActivity.this,"Please provide a valid city!",Toast.LENGTH_LONG);
toast.show();
}
}
}
}
public class DayAdapter extends ArrayAdapter<String>
{
private static final String TAG = "DayAdapter";
private Context context;
private LayoutInflater layoutInflater;
private int layoutresourceID;
private ArrayList<String> dayBlock;
private ArrayList<WeatherData> dayWeather, weatherBlock;
JsonToWeatherData json = new JsonToWeatherData();
public DayAdapter(@NonNull Context context, int resource, @NonNull ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock)
{
super(context, resource, dayBlock);
this.context = context;
this.dayBlock = dayBlock;
this.weatherBlock = weatherBlock;
layoutInflater = LayoutInflater.from(context);
this.layoutresourceID = resource;
if (weatherBlock == null)
{
Log.e(TAG, "DayAdapter: full block is null");
}
}
@Override
public int getCount()
{
return dayBlock.getSize();
}
public void UpdateData(@NonNull ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock)
{
this.dayBlock = dayBlock;
this.weatherBlock = weatherBlock;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent)
{
if (convertView == null)
{
convertView = layoutInflater.inflate(layoutresourceID,parent,false);
}
if (weatherBlock == null)
{
Log.d(TAG, "getView: weatherBlock is null");
return convertView;
}
TextView date = (TextView) convertView.findViewById(R.id.date);
TextView minTempFoDay = (TextView) convertView.findViewById(R.id.minTempOfDay);
TextView maxTempFoDay = (TextView) convertView.findViewById(R.id.maxTempOfDay);
ListView weatherHolderListView = (ListView) convertView.findViewById(R.id.wHoldLV);
String dateString = dayBlock.get(position);
dayWeather = json.extractByDate(weatherBlock, dateString);
if (dayWeather == null)
{
Log.d(TAG, "getView: dayweather array is null");
return convertView;
}
if (position > dayWeather.getSize() - 1)
{
Log.d(TAG, "getView: the position is too great for the dayWeather array");
return convertView;
}
String test = dayWeather.get(position).getTemp(); // error occured here
Log.d(TAG, "getView: test string : " + test);
date.setText(dateString);
DecimalFormat df = new DecimalFormat(".##");
float mint = 500, maxt = 0;
String mint1 = "", maxt1 = "";
for (WeatherData data : dayWeather)
{
if (mint > Float.parseFloat(data.getMinTemp()))
{
mint = Float.parseFloat(data.getMinTemp());
mint1 = df.format(mint);
Log.d(TAG, "getView: mint : " + mint);
}
if (maxt > Float.parseFloat(data.getMaxTemp()))
{
maxt = Float.parseFloat(data.getMaxTemp());
maxt1 = df.format(maxt);
}
}
minTempFoDay.setText(mint1);
maxTempFoDay.setText(maxt1);
WeatherAdapter weatherAdapter = new WeatherAdapter(context, R.layout.weather_holder, dayWeather);
weatherHolderListView.setAdapter(weatherAdapter);
return convertView;
}
}
，类似的事情可能满足您的需求：
UPDATE对于update this_table tt set
tt.standardid = (select s.standardid
from standard s
where s.standard_name = :some_unique_standard_name
),
tt.courseid = (select c.courseid
from course c
where c.course_name = :some_unique_course_name
)
where tt.registrationid = :some_registration_id;
：
INSERTinsert into this_table
(registrationid, standardid, courseid, marks)
select
:some_registration_id,
(select s.standardid
from standard s
where s.standard_name = :some_unique_standard_name
),
(select c.courseid
from course c
where c.course_name = :some_unique_course_name
),
:marks_value
from dual;
）代表一个变量您需要提供其值:，因为其他地方可能没有INSERT表）。