我有一个问题，关于如何在保留现有数据的同时更改Oracle数据库中的故事之间的关系。
假设我想代表人和雇主，以便每个人都为一个雇主工作。我使用PERSON表和EMPLOYER表执行此操作，该表与EMPLOYER与PERSON的1：M关系。 PERSON表具有列ID，NAME和EMPLOYER_ID，EMPLOYER表具有列ID，NAME和AND LOCATION。
如果我想更新此架构，以便PERSON可以为多个EMPLOYER工作，我可以添加一个PERSON_EMPLOYER表，其中包含每个ID的列。
有没有人可以指出最合理的方法来移动我现有的数据呢？我想我可以添加一个联接表，但我不确定如何用现有雇主填充它：雇主数据。之后我猜我从PERSON中删除了EMPLOYER_ID列。
我应该只是备份数据库并在脚本中执行此操作吗？
非常感谢你。
答案 0 :(得分：0)
备份总是一个好主意。 但在我看来，将数据从一个表传输到另一个表是非常可靠的操作。您没有必要制作脚本，只需一步一步地检查更改。
要将数据从PERSON表传输到PERSON_EMPLOYER表，您可以使用简单的INSERT
public class MapActivity extends FragmentActivity implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener,GoogleMap.OnInfoWindowClickListener{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map);
// int x =_st.jsonArray.length();
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
checkLocationPermission();
}
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
fragmentOnMap = (FragmentOnMap)getFragmentManager().findFragmentById(R.id.fragment_bottom);
getFragmentManager().beginTransaction().hide(fragmentOnMap);
}
@Override
public void onMapReady(GoogleMap googleMap) {
//Get Last Known Location and convert into Current Longitute and Latitude
final LocationManager mlocManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
final Location currentGeoLocation = mlocManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
double currentLat = currentGeoLocation.getLatitude();
double currentLon = currentGeoLocation.getLongitude();
LatLng currentLatLng = new LatLng(currentLat,currentLon);
//Toast.makeText(this,"Cur Lat" +currentLat+"Lon"+currentLon,Toast.LENGTH_LONG).show();
// Get JSON String and Break it down into individual nodes
//double x=_location.getLatitude();
//double y=_location.getLongitude();
json_string = getIntent().getExtras().getString("JSON_DTA");
LatLng latLng = null;
try {
int count = 0;
//jsonObject = new JSONObject(json_string);
jsonArray = new JSONArray(json_string);
while (count < jsonArray.length()) {
JSONObject JO = jsonArray.getJSONObject(count);
_id = JO.getInt("id");
_doctorname = JO.getString("doctorname");
_doclat = JO.getString("latitude");
_doclong = JO.getString("longitude");
count++;
Double d = Double.parseDouble(_doclat);
Double e = Double.parseDouble(_doclong);
latLng = new LatLng(d, e);
DecimalFormat df = new DecimalFormat("####0.0");
DistanceBetweenPoints distanceBetweenPoints = new DistanceBetweenPoints();
double distance = distanceBetweenPoints.CalculationByDistance(currentLatLng,latLng);
double distanceThreshHold = 7 ;
if(distance < distanceThreshHold )
{
mMap = googleMap;
mMap.setOnInfoWindowClickListener(this);
MarkerOptions _markeroptions = new MarkerOptions()
.position(latLng)
.title(_doctorname+": " + df.format(distance) + " KM" )
.icon(BitmapDescriptorFactory.fromResource(R.drawable.smallest_logo));
mMap.addMarker(_markeroptions);
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
}
else
{
mMap = googleMap;
}
}
} catch (JSONException e) {
e.printStackTrace();
}
//Initialize Google Play Services
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
} else {
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
}
protected synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mGoogleApiClient.connect();
}
@Override
public void onConnected(@Nullable Bundle bundle) {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(1000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onLocationChanged(Location location) {
mLastLocation = location;
if (mCurrLocationMarker != null) {
mCurrLocationMarker.remove();
}
//Place current location marker
LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
MarkerOptions markerOptions = new MarkerOptions();
markerOptions.position(latLng);
markerOptions.title("Current Position");
markerOptions.draggable(true);
markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
mCurrLocationMarker = mMap.addMarker(markerOptions);
// Toast.makeText(this, "Current" + latLng, Toast.LENGTH_LONG).show();
String tag = null;
Log.d(tag, "lon: " + location.getLongitude() + " ----- lat: " + location.getLatitude());
//move map camera
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mMap.animateCamera(CameraUpdateFactory.zoomTo(11));
//stop location updates
if (mGoogleApiClient != null) {
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
}
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
public boolean checkLocationPermission(){
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Asking user if explanation is needed
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION)) {
// Show an expanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
return false;
} else {
return true;
}
}
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_LOCATION: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission was granted.
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
if (mGoogleApiClient == null) {
buildGoogleApiClient();
}
mMap.setMyLocationEnabled(true);
}
} else {
// Permission denied, Disable the functionality that depends on this permission.
Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
}
return;
}
// other 'case' lines to check for other permissions this app might request.
//You can add here other case statements according to your requirement.
}
}
不要忘记COMMIT这个操作！