是否有可能适用的主键在Android的数据库中的文本字段有可能、字段、数据库中、主键
我创建了一个简单的表，其中包含姓名和电子邮件ID的人员的。当我给了创建这样的查询：
I have created a simple table that contains the name and email id's of the persons. When i am giving the create query like this:
创建表的联系人（name文本不为空，电子邮件文本主键NOT NULL）;
不过，这是行不通的。运行，也没有主键工作时我没有得到任何异常或错误。虽然使用SQLite的浏览器在浏览表我观察，目前只有四种数据类型：
But this is not working. I'm not getting any exception or error while running nor the primary key is working. While browsing the table using SQLite browser i observed that there are only four data types:
是否有可能适用于主键只在整数？是这样的，如果我想要在文本字段主键。谢谢。这是code，我用：
Is it possible to apply primary key only on integer? What is the case if i want primary key on text fields. Thank you. This is the code that i used:
公共类DBAdapter {
public class DBAdapter {
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_EMAIL = "email";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "MyDB";
private static final String DATABASE_TABLE = "contacts";
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_CREATE =
"create table contacts (_id integer primary key autoincrement, "
+ "name text not null, email text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
try {
db.execSQL(DATABASE_CREATE);
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS contacts");
onCreate(db);
}
}
//---opens the database---
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
//---insert a contact into the database---
public long insertContact(String name, String email)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_EMAIL, email);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//---deletes a particular contact---
public boolean deleteContact(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//---retrieves all the contacts---
public Cursor getAllContacts()
{
return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME,
KEY_EMAIL}, null, null, null, null, null);
}
//---retrieves a particular contact---
public Cursor getContact(long rowId) throws SQLException
{
Cursor mCursor =
db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
KEY_NAME, KEY_EMAIL}, KEY_ROWID + "=" + rowId, null,
null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---updates a contact---
public boolean updateContact(long rowId, String name, String email)
{
ContentValues args = new ContentValues();
args.put(KEY_NAME, name);
args.put(KEY_EMAIL, email);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}
}
推荐答案
根据在 常见问题解答 源码文件，使用文本为数据类型的主键应该工作。
as per the faq of sqlite documentation, using TEXT as a datatype for primary key should work.
我用您的查询，这里是，在创建表。
i used your query and here it is, the table is created.
CREATE TABLE contacts ( email text primary key not null, name text not null);
INSERT INTO contacts VALUES ('sample@email.com', 'sample')
INSERT INTO contacts VALUES ('people@email.com', 'sample')
现在这里是哪里出了问题。
now here is where it went wrong.
当我跑这又
INSERT INTO contacts VALUES ('sample@email.com', 'sample')
什么都没有发生，没有错误。 但它并没有更新记录。所以我的结论数据的完整性是有，但你没有得到有关失败的任何反馈
nothing happened, no errors. But it did not update the record. so i conclude data integrity is there but you don't get any feedback about the failure.
