我有两张桌子。如果表A中的百分比为null，那么我想在表B中查找它
02-03 09:59:18.475 2566-2566/com.mycompany.mapsdemo E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mycompany.mapsdemo, PID: 2566
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mycompany.mapsdemo/com.mycompany.mapsdemo.MapsActivity}: android.view.InflateException: Binary XML file line #1: Binary XML file line #1: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.view.InflateException: Binary XML file line #1: Binary XML file line #1: Error inflating class fragment
at android.view.LayoutInflater.inflate(LayoutInflater.java:539)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:393)
at android.app.Activity.setContentView(Activity.java:2166)
at com.mycompany.mapsdemo.MapsActivity.onCreate(MapsActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.view.InflateException: Binary XML file line #1: Error inflating class fragment
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:782)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:393)
at android.app.Activity.setContentView(Activity.java:2166)
at com.mycompany.mapsdemo.MapsActivity.onCreate(MapsActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.io.File.mkdir()' on a null object reference
at com.google.maps.api.android.lib6.gmm6.m.ad.a(Unknown Source)
at com.google.maps.api.android.lib6.gmm6.c.h.a(Unknown Source)
at com.google.maps.api.android.lib6.gmm6.c.ao.a(Unknown Source)
at com.google.maps.api.android.lib6.e.bd.a(Unknown Source)
at com.google.maps.api.android.lib6.e.ev.a(Unknown Source)
at com.google.maps.api.android.lib6.e.z.a(Unknown Source)
at com.google.maps.api.android.lib6.e.y.a(Unknown Source)
at com.google.android.gms.maps.internal.u.onTransact(SourceFile:107)
at android.os.Binder.transact(Binder.java:387)
at com.google.android.gms.maps.internal.IMapFragmentDelegate$zza$zza.onCreateView(Unknown Source)
at com.google.android.gms.maps.SupportMapFragment$zza.onCreateView(Unknown Source)
at com.google.android.gms.dynamic.zza$4.zzb(Unknown Source)
at com.google.android.gms.dynamic.zza.zza(Unknown Source)
at com.google.android.gms.dynamic.zza.onCreateView(Unknown Source)
at com.google.android.gms.maps.SupportMapFragment.onCreateView(Unknown Source)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1036)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1226)
at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1328)
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2284)
at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:111)
at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:314)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:31)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
at android.view.LayoutInflater.
答案 0 :(得分：1)
这应该这样做：
SELECT t.id, COALESCE(t.percentage, s.percentage) AS percentage
FROM project_percentage t
LEFT OUTER JOIN
test2 AS s
ON s.id = t.id;