Android “SELECT last_insert_rowid()”总是返回“0”
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"SELECT last_insert_rowid()" returns always "0"
提问by venni
I have a problem with "last_insert_rowid()".
我对“last_insert_rowid()”有疑问。
In my DB-Helper-Class I am doing the following:
在我的 DB-Helper-Class 中，我正在执行以下操作：
public int getLastID() {
final String MY_QUERY = "SELECT last_insert_rowid() FROM "+ DATABASE_TABLE5;
Cursor cur = mDb.rawQuery(MY_QUERY, null);
cur.moveToFirst();
int ID = cur.getInt(0);
cur.close();
return ID;
}
But when I call this in my intent:
但是当我按照我的意图调用它时：
int ID = mDbHelper.getLastID();
Toast.makeText(this, "LastID: " + ID, Toast.LENGTH_SHORT).show();
I get always "0" back. That can not be, cause I have a lot of entries in my DB and the autoincrement value should be much higher.
我总是得到“0”回来。那不可能，因为我的数据库中有很多条目，并且自动增量值应该高得多。
What I am doing wrong?
我做错了什么？
回答by venni
OK, that was the right hint John ;-)
好的，这是正确的提示约翰 ;-)
The query should look like this:
查询应如下所示：
public int getHighestID() {
final String MY_QUERY = "SELECT MAX(_id) FROM " + DATABASE_TABLE5;
Cursor cur = mDb.rawQuery(MY_QUERY, null);
cur.moveToFirst();
int ID = cur.getInt(0);
cur.close();
return ID;
}
回答by Ali
You don't need to put table name with last_insert_rowid()it will automatically select last inserted id from session. so you can just simply use this function as well.
您不需要将表名与last_insert_rowid()它会自动从会话中选择最后插入的 id。所以你也可以简单地使用这个功能。
public int getHighestID() {
final String MY_QUERY = "SELECT last_insert_rowid()";
Cursor cur = mDb.rawQuery(MY_QUERY, null);
cur.moveToFirst();
int ID = cur.getInt(0);
cur.close();
return ID;
}
