问题
I ran into the Foreign Key Constraint Failed (code 787) error when I tried to upgrade my database. The only change I did was try to add a 4th entry to my InsertStatus. I looked around and I read that using ON DELETE CASCADE should solve my problem so I tried placing it at all my FK references and tried again but still the same problem.
Logcat points to my onUpgrade and all the DROP TABLES in it ( i tried removing it one at a time to see which ones were bad and apparently all of them were ).
Am I using ON DELETE CASCADE wrong? Or is it something else in my code?
InsertStatus
void InsertStatus(SQLiteDatabase db) {
ContentValues cv = new ContentValues();
cv.put(colStatusID, 0);
cv.put(colStatClass, "Active");
db.insert(statTable, colStatusID, cv);
cv.put(colStatusID, 1);
cv.put(colStatClass, "Settled");
db.insert(statTable, colStatusID, cv);
cv.put(colStatusID, 2);
cv.put(colStatClass, "Terminated");
db.insert(statTable, colStatusID, cv);
cv.put(colStatusID, 3);
cv.put(colStatClass, "");
db.insert(statTable, colStatusID, cv);
}
DatabaseHelper
db.execSQL("CREATE TABLE " + termsTable + " (" + colTermsID + " INTEGER PRIMARY KEY , " + colTermsClass + " TEXT)");
db.execSQL("CREATE TABLE " + periodTable + " (" + colPeriodID + " INTEGER PRIMARY KEY , " + colPeriodClass + " TEXT)");
db.execSQL("CREATE TABLE " + statTable + " (" + colStatusID + " INTEGER PRIMARY KEY , " + colStatClass + " TEXT)");
db.execSQL("CREATE TABLE " + accountsTable + " (" + colID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
colName + " TEXT, " +
colAmount + " Integer, " +
colPurpose + " TEXT, " +
colTerms + " INTEGER NOT NULL, " +
colPeriod +" INTEGER NOT NULL, " +
colBalance +" INTEGER, "+
colStatus + " INTEGER DEFAULT '1'," +
colDate + " TEXT, " +
colEditDate + " TEXT, " +
"FOREIGN KEY (" + colTerms + ") REFERENCES " + termsTable + " (" + colTermsID + ") ON DELETE CASCADE," +
"FOREIGN KEY (" + colPeriod + ") REFERENCES " + periodTable + " (" + colPeriodID + ") ON DELETE CASCADE," +
"FOREIGN KEY (" + colStatus + ") REFERENCES " + statTable + " (" + colStatusID + ") ON DELETE CASCADE);");
db.execSQL("CREATE TABLE " + payTable + " (" + colPayID + " INTEGER PRIMARY KEY , " +
colGroupID + " INTEGER NOT NULL, " +
colPayBal + " TEXT, " +
colInterest + " TEXT, " +
colPayDue + " TEXT, " +
colDateDue + " TEXT, " +
colPaid + " Integer, " +
"FOREIGN KEY (" + colGroupID + ") REFERENCES " + accountsTable + " (" + colID + ") ON DELETE CASCADE);");
db.execSQL("CREATE VIEW " + viewAccs +
" AS SELECT " + accountsTable + "." + colID + " AS _id," +
" " + accountsTable + "." + colName + "," +
" " + accountsTable + "." + colAmount + "," +
" " + accountsTable + "." + colPurpose + "," +
" " + termsTable + "." + colTermsClass + "," +
" " + periodTable + "." + colPeriodClass + "," +
" " + accountsTable+ "." + colBalance + "," +
" " + statTable + "." + colStatClass + "," +
" " + accountsTable + "." + colDate + "," +
" " + accountsTable + "." + colEditDate + "" +
" FROM " + accountsTable +
" JOIN " + termsTable + " ON " + accountsTable + "." + colTerms + " = " + termsTable + "." + colTermsID +
" JOIN " + periodTable + " ON " + accountsTable + "." + colPeriod + " = " + periodTable + "." + colPeriodID +
" JOIN " + statTable + " ON " + accountsTable + "." + colStatus + " = " + statTable + "." + colStatusID );
db.execSQL("CREATE VIEW " + viewPmnts +
" AS SELECT " + payTable + "." + colPayID + " AS _id," +
" " + accountsTable + "." + colID + "," +
" " + payTable + "." + colGroupID + "," +
" " + payTable + "." + colPayBal + "," +
" " + payTable + "." + colInterest + "," +
" " + payTable + "." + colPayDue + "," +
" " + payTable + "." + colDateDue + "," +
" " + payTable + "." + colPaid + "" +
" FROM " + payTable +
" JOIN " + accountsTable + " ON " + payTable + "." + colGroupID + " = " + accountsTable + "." + colID );
InsertTerms(db);
InsertPeriods(db);
InsertStatus(db);
}
onUpgrade
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + accountsTable);
db.execSQL("DROP TABLE IF EXISTS " + termsTable);
db.execSQL("DROP TABLE IF EXISTS " + periodTable);
db.execSQL("DROP TABLE IF EXISTS " + statTable);
db.execSQL("DROP TABLE IF EXISTS " + payTable);
db.execSQL("DROP TRIGGER IF EXISTS acc_id_trigger");
db.execSQL("DROP TRIGGER IF EXISTS acc_id_trigger22");
db.execSQL("DROP TRIGGER IF EXISTS fk_accterm_termid");
db.execSQL("DROP TRIGGER IF EXISTS fk_accperiod_periodid");
db.execSQL("DROP TRIGGER IF EXISTS fk_accpay_payid");
db.execSQL("DROP TRIGGER IF EXISTS fk_accstat_statid");
db.execSQL("DROP VIEW IF EXISTS " + viewAccs);
db.execSQL("DROP VIEW IF EXISTS " + viewPmnts);
onCreate(db);
}
回答1:
According to the below link you insert the value which failed the constraints of foreign key means you added a value of foregin key which not exists in parent table
https://www.sqlite.org/foreignkeys.html
回答2:
The error here is related to creating a child entity before their parent is in existence.
The Flow should be:
--Create Parent and get parent ID. ---- Create child entity containing a reference to parent ID.
So If you create a child entity without first having a valid parent ID you will be thrown this fatal error.
回答3:
In my case I forgot to fill a parent table with data. When added an item to child table, got this error. When removed foreignKeys lines in Entity-file:
foreignKeys = [
ForeignKey(entity = SomeEntity::class, parentColumns = ["id"], childColumns = ["parent_id"]),
...
]
insertion became possible. (But if you do that without clearing app data, you will get an exception java.lang.IllegalStateException: Room cannot verify the data integrity. Looks like you've changed schema but forgot to update the version number. You can simply fix this by increasing the version number.)
So, simply add necessary data to parent tables.
UPDATE
I got this exception again.
In order to test which foreign key is conficting, comment several of them and recompile the application. Also delete installed one or wipe it's data. After starting the app execute requests as usual. If no exception happened, uncomment one foreign key. Then delete the app again, recompile, add data to the table. Do it until you know which foreign key is violated.
In my case I inserted 0 instead of null into a column, so that a parent table didn't contain 0.
回答4:
Make sure that you first insert the object which is in the parent table. I was doing the same mistake while making some tests (not adding the corresponding parent, so that PK from the parent table was non existing.)
回答5:
In my situation problem was that I used
@Insert(onConflict = OnConflictStrategy.REPLACE)
instead
@Update
in @Dao.
来源：https://stackoverflow.com/questions/29341380/sqlite-foreign-key-constraint-failed-code-787