SQlite - Android - Foreign key syntax
I've been trying to get foreign keys开发者_开发百科 working within my Android SQLite database. I have tried the following syntax but it gives me a force close:
private static final String TASK_TABLE_CREATE = "create table "
+ TASK_TABLE + " (" + TASK_ID
+ " integer primary key autoincrement, " + TASK_TITLE
+ " text not null, " + TASK_NOTES + " text not null, "
+ TASK_DATE_TIME + " text not null, FOREIGN KEY ("+TASK_CAT+") REFERENCES "+CAT_TABLE+" ("+CAT_ID+"));";
Any ideas what I might be doing wrong? if you need to see the other table structure then I can, its just a very simple structure for the second with an ID and a name.
Edit:
Here is the error:
03-13 13:42:35.389: ERROR/AndroidRuntime(312): Caused by: android.database.sqlite.SQLiteException: unknown column "taskCat" in foreign key definition: create table reminders (_id integer primary key autoincrement, task_title text not null, notes text not null, reminder_date_time text not null, FOREIGN KEY (taskCat) REFERENCES category (_id));
You have to define your TASK_CAT
column first and then set foreign key on it.
private static final String TASK_TABLE_CREATE = "create table "
+ TASK_TABLE + " ("
+ TASK_ID + " integer primary key autoincrement, "
+ TASK_TITLE + " text not null, "
+ TASK_NOTES + " text not null, "
+ TASK_DATE_TIME + " text not null,"
+ TASK_CAT + " integer,"
+ " FOREIGN KEY ("+TASK_CAT+") REFERENCES "+CAT_TABLE+"("+CAT_ID+"));";
More information you can find on sqlite foreign keys doc.
Since I cannot comment, adding this note in addition to @jethro answer.
I found out that you also need to do the FOREIGN KEY line as the last part of create the table statement, otherwise you will get a syntax error when installing your app. What I mean is, you cannot do something like this:
private static final String TASK_TABLE_CREATE = "create table "
+ TASK_TABLE + " (" + TASK_ID
+ " integer primary key autoincrement, " + TASK_TITLE
+ " text not null, " + TASK_NOTES + " text not null, "
+ TASK_CAT + " integer,"
+ " FOREIGN KEY ("+TASK_CAT+") REFERENCES "+CAT_TABLE+" ("+CAT_ID+"), "
+ TASK_DATE_TIME + " text not null);";
Where I put the TASK_DATE_TIME after the foreign key line.
As you can see in the error description your table contains the columns (_id, tast_title, notes, reminder_date_time) and you are trying to add a foreign key from a column "taskCat" but it does not exist in your table!
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