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<span style="font-size:14px;">public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK = "create table book ("
+ "id integer primary key autoincrement, "
+ "author text, "
+ "price real, "
+ "pages integer, "
+ "name text)";
private Context mContext;
public MyDatabaseHelper(Context context, String name, CursorFactory
factory, int version) {
super(context, name, factory, version);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}</span>2 升级数据库package com.example.sqllitehelp;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;
public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK="create table Book ("
+"id integer primary key autoincrement ,"
+"author test , "
+"price real , "
+"pages integer , "
+"name text) "
;
public static final String CREATE_CATEGORY="create table Category ("
+"id integer primary key autoincrement ,"
+"category_name test , "
+"category_code integer)"
;
private Context mContext;
public MyDatabaseHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
mContext=context;
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
Toast.makeText(mContext, "create successed", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("drop table if exists Book");
db.execSQL("drop table if exists Category");
onCreate(db);
Toast.makeText(mContext, "删除数据", Toast.LENGTH_SHORT).show();
}
}
MyDatabaseHelper(context, "BookStore.db", null, 1); 把这里的版本号改成2就可以执行升级方法了public class MainActivity extends Activity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
??
Button addData = (Button) findViewById(R.id.add_data);
addData.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
// 开始组装第一条数据
values.put("name", "The Da Vinci Code");
values.put("author", "Dan Brown");
values.put("pages", 454);
values.put("price", 16.96);
db.insert("Book", null, values); // 插入第一条数据
values.clear();
// 开始组装第二条数据
values.put("name", "The Lost Symbol");
values.put("author", "Dan Brown");
values.put("pages", 510);
values.put("price", 19.95);
db.insert("Book", null, values); // 插入第二条数据
}
});
}
}4 更新数据public class MainActivity extends Activity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
??
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("price", 10.99);
db.update("Book", values, "name = ?", new String[] { "The Da
Vinci Code" });
}
});
}
}db.update("Book", values, "name = ?", new String[] { "The DaVinci Code" }) 这句话相当于 Update Book set price=10.99 where name=’The DaVinci Code"‘<span style="font-size:14px;">public class MainActivity extends Activity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
??
Button deleteButton = (Button) findViewById(R.id.delete_data);
deleteButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete("Book", "pages > ?", new String[] { "500" });
}
});
}
}</span> db.delete("Book", "pages > ?", new String[] { "500" }); 相当于 delete from Book where pages>500public class MainActivity extends Activity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
??
Button queryButton = (Button) findViewById(R.id.query_data);
queryButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
// 查询Book 表中所有的数据
Cursor cursor = db.query("Book", null, null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
// 遍历Cursor 对象，取出数据并打印
String name = cursor.getString(cursor.
getColumnIndex("name"));
String author = cursor.getString(cursor.
getColumnIndex("author"));
int pages = cursor.getInt(cursor.getColumnIndex
("pages"));
double price = cursor.getDouble(cursor.
getColumnIndex("price"));
Log.d("MainActivity", "book name is " + name);
Log.d("MainActivity", "book author is " + author);
Log.d("MainActivity", "book pages is " + pages);
Log.d("MainActivity", "book price is " + price);
} while (cursor.moveToNext());
}
cursor.close();
}
});
}
}7 使用 SQL 操作数据库<span style="font-size:14px;">public class MainActivity extends Activity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
??
Button replaceData = (Button) findViewById(R.id.replace_data);
replaceData.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.beginTransaction(); // 开启事务
try {
db.delete("Book", null, null);
if (true) {
// 在这里手动抛出一个异常，让事务失败
throw new NullPointerException();
}
ContentValues values = new ContentValues();
values.put("name", "Game of Thrones");
values.put("author", "George Martin");
values.put("pages", 720);
values.put("price", 20.85);
db.insert("Book", null, values);
db.setTransactionSuccessful(); // 事务已经执行成功
} catch (Exception e) {
e.printStackTrace();
} finally {
db.endTransaction(); // 结束事务
}
}
});
}
</span><span style="font-size:18px;color:#ff0000;">}</span>8. 2升级数据库的最佳写法public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK = "create table Book ("
+ "id integer primary key autoincrement, "
+ "author text, "
+ "price real, "
+ "pages integer, "
+ "name text)";
public MyDatabaseHelper(Context context, String name, CursorFactory
factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}不过，几星期之后又有了新需求，这次需要向数据库中再添加一张 Category 表。于是，修改 MyDatabaseHelper 中的代码，如下所示：public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK = "create table Book ("
+ "id integer primary key autoincrement, "
+ "author text, "
+ "price real, "
+ "pages integer, "
+ "name text)";
public static final String CREATE_CATEGORY = "create table Category ("
+ "id integer primary key autoincrement, "
+ "category_name text, "
+ "category_code integer)";
public MyDatabaseHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
switch (oldVersion) {
case 1:
db.execSQL(CREATE_CATEGORY);
default:
}
}
}是没过多久，新的需求又来了，这次要给 Book 表和 Category 表之间建立关联，需要在 Book 表中添加一个 category_id 的字段。再次修改 MyDatabaseHelper 中的代码，如下所示public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK = "create table Book ("
+ "id integer primary key autoincrement, "
+ "author text, "
+ "price real, "
+ "pages integer, "
+ "name text, "
+ "category_id integer)";
public static final String CREATE_CATEGORY = "create table Category ("
+ "id integer primary key autoincrement, "
+ "category_name text, "
+ "category_code integer)";
public MyDatabaseHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
switch (oldVersion) {
case 1:
db.execSQL(CREATE_CATEGORY);
case 2:
db.execSQL("alter table Book add column category_id integer");
default:
}
}
}可以看到，首先我们在 Book 表的建表语句中添加了一个 category_id 列，这样当用户直Android基础之十四数据存储 之 SQLite数据库详解
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原文地址：http://blog.csdn.net/zhupengqq/article/details/51436427
