尝试在Android中的sqlite中更新最后一条记录中的某个列

Question

I have a db that is structred as such

uid | username | password |     email   | cur_level
1     default      abc123   me@email.com    0

In my game after you complete a level in the main activity I run a method called increase_current_level() value++; test_db.open(); test_db.updateLevel(value); cur_level = value; test_db.close();

So that seems to work with no problems but when test_db.updateLevel(value) is run, that when the program crashes.

In my DBHelper the code for update level is as follows.

public boolean updateLevel(String level) {
        ContentValues args = new ContentValues();

        args.put(KEY_CUR_LEVEL, level);
        return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "="
                + "WHERE id=(SELECT max(id) FROM DATABASE_TABLE)", null) > 0;

    }

My log cat error seems to be:

10-17 17:36:10.833: E/AndroidRuntime(1815): Caused by: android.database.sqlite.SQLiteException: near "WHERE": syntax error (code 1): , while compiling: UPDATE test SET cur_level=? WHERE _id=WHERE id=(SELECT max(id) FROM DATABASE_TABLE)

I'm very new to SQLite so, it's kind of intimidating, but I hope someone sees a very obvious flaw. Thanks

Update 1:

My updated code:

public boolean updateLevel(String level) {
    ContentValues args = new ContentValues();

    args.put(KEY_CUR_LEVEL, level);
    return mDb.update(DATABASE_TABLE, args, KEY_ROWID + " = (SELECT max(id) FROM DATABASE_TABLE",
            null) > 0;

}

Updated error msg:

10-17 18:26:50.804: E/AndroidRuntime(3684): Caused by: android.database.sqlite.SQLiteException: near "DATABASE_TABLE": syntax error (code 1): , while compiling: UPDATE test SET cur_level=? WHERE _id = (SELECT max(id) FROM DATABASE_TABLE

Answer 1

From your code, your WHERE clause is probably malformed. Shouldn't it be

"WHERE id=(SELECT max(id) FROM " + DATABASE_TABLE

instead of

"WHERE id=(SELECT max(id) FROM DATABASE_TABLE)"

?

Answer 2

The syntax of mDb.update is

update(table, ContentValues values, String whereClause, String[] whereArgs)

Let's assume that KEY_ROWID = "id"

For your whereClause , you're literally passing

"id = WHERE id = (SELECT max(id) FROM DATABASE_TABLE"

which is not valid SQL.

You don't seem to need " id = ". Just start your WHERE clause with " WHERE id= "

However, your question implies that you have only one record in the DB. Why use a DB for one record? And if you have more than one record in it, you should use a WHERE clause that searches on something unique, rather than using SELECT max(id) .

The bottom line is that you need to improve your knowledge of SQL.

Answer 3

The update function already puts a WHERE into the query, and you have duplicated the column name ( KEY_ROWID and "id" ). Use:

mDb.update(..., KEY_ROWID + "= (SELECT ...)");

Answer 4

If your table only has one row then you don't need a WHERE clause. The following statement should update all rows in your table. If only one record exists this will solve your problem.

return mDb.update(DATABASE_TABLE, args, null, null) > 0;

If more than one row exists you will need to know the uid of the row you want to update prior to calling the update function. In which case it would look like this...

String dbID = "the unique id of the row you want to update";

return mDb.update(DATABASE_TABLE, args, "id=?", new String[]{dbID}) > 0;

Hope this helps.