Android 如何从游标中获取行 ID

how to get a row ID from a Cursor

提问by oriharel

How do I get the row ID from a Cursor?

如何从 Cursor 获取行 ID？

回答by Nic Strong

I don't think the Cursor exposes this directly.
SQLiteDatabase.insert()returns the row id of the newly inserted row. Or in Android the convention is that there is a column named "_id"that contains the primary autoincrement key of the table. So cursor.getLong(cursor.getColumnIndex("_id"))would retrieve this.

我认为 Cursor 不会直接暴露这一点。
SQLiteDatabase.insert()返回新插入行的行 ID。或者在 Android 中，约定是有一个名为的列"_id"包含表的主要自动增量键。所以cursor.getLong(cursor.getColumnIndex("_id"))会检索这个。

回答by Luigi Putanesca

I had this same problem where the column index for the primary key was reported as -1 (meaning it isn't there). The problem was that I forgot to include the _ID column in the initial SELECT clause that created the cursor. Once I made sure it was included, the column was accessible just like any of the others.

我遇到了同样的问题，其中主键的列索引报告为 -1（意味着它不存在）。问题是我忘记在创建游标的初始 SELECT 子句中包含 _ID 列。一旦我确定它被包含在内，该列就可以像其他任何列一样访问。

回答by CP Taylor

Concerning the last sentence of Nic Strong's answer,following command didn't work for me. cursor.getColumnIndex("_id")was still -1

关于 Nic Strong 回答的最后一句话，以下命令对我不起作用。cursor.getColumnIndex("_id")仍然是-1

 cursor.getLong(cursor.getColumnIndex("_id"))

Maybe there's some other issue in my configuration that's causing the problem?

也许我的配置中还有其他一些问题导致了这个问题？

Personally I've taken to maintaining my own custom unique id column in each table I create; A pain, but it gets around this issue.

我个人已经开始在我创建的每个表中维护我自己的自定义唯一 id 列；一个痛苦，但它解决了这个问题。

回答by Arkadiusz Cie?liński

return sqlite_db.query(table, new String[] { "rowid", "*" }, where, args, null, null, null);

In my case I have "rowid" in DataManager.FIELD_ID and this is SQLite identity column (each table in sqlite has this special kind of column), so I don't need any of my own custom unique id column in tables.

在我的情况下，我在 DataManager.FIELD_ID 中有“rowid”，这是 SQLite 标识列（sqlite 中的每个表都有这种特殊类型的列），所以我不需要表中任何我自己的自定义唯一 id 列。

回答by Ferran Maylinch

Cursor cursor = mySQLiteHelper.getReadableDatabase().query(TABLE_NAME, new String[] { "ROWID", "*" }, where, null, null, null, null);

then

然后

long rowId = cursor.getLong(0);

回答by MikeT

As long as the TABLE is not defined using WITHOUT ROWIDyou can get the ROWID(or should that be rowidsee below for case) if you specify it as a column to be retrieved.

只要 TABLE 没有使用定义，如果您将其指定为要检索的列，WITHOUT ROWID您就可以获得ROWID（或者应该是rowid，请参见下面的案例）。

For example for a table with 3 defined columns (Names, Colour and Age) with no conventional _idcolumn. The following rawQuery works and returns the ROWID:-

例如，对于具有 3 个已定义列（名称、颜色和年龄）且没有常规_id列的表。以下 rawQuery 工作并返回ROWID：-

Cursor csr = db.rawQuery("SELECT Names, Colour, Age, ROWID FROM " + TABLE_NAME,null);

Note! that the column name in the cursor is lowercaseas per :-

笔记！游标中的列名是小写的，如下所示：-

Note! ROWIDin the SELECT SQLis case independent (e.g. RoWiD works).

笔记！SELECT SQL中的ROWID与大小写无关（例如 RoWiD 工作）。

Using

使用

Cursor csr = db.rawQuery("SELECT * FROM " + TABLE_NAME,null);

WILL NOTreturn the ROWID(likewise for null for the columns when using the querymethod).

不会返回ROWID（对于使用该query方法时列的 null 也是如此 ）。

Using query(as opposed to rawQuery) works in the same way, that is you need to specifiy ROWID (note alternatives to ROWID below) as a column to be retrieved e.g. :-

使用query(而不是rawQuery) 的工作方式相同，即您需要指定 ROWID（注意下面 ROWID 的替代方案）作为要检索的列，例如：-

Cursor csr = db.query(TABLE_NAME,new String[]{
                "OiD",
                "Names",
                "Colour",
                "Age"
        },null,null,null,null,null);

---

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Alternatives to ROWID

ROWID 的替代品

Instead of ROWID, you can also use _ROWID_or OID(case independent) as the column name in the query noting that the column name in the resultant cursor is rowidi.e. it is lowercase.

代替ROWID，您还可以使用_ROWID_or OID（大小写无关）作为查询中的列名，注意结果游标中的列名是rowid ，即它是小写的。