SQLiteDatabase 的使用

本文主要是介绍SQLiteDatabase 的使用，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

功能]

SQLiteDatabase 是关于数据库操作的 可用于 insert delete update query 等操作 可惜美中不足的是：

1. 其不支持创建数据库

2. 其不支持版本更新 或者说其不知道如何做 因为具体数据的差异



鉴于以上的缺陷 有一个辅助类可以完成上面功能 那就是：SQLiteOpenHelper





[代码]

1. 定义SQLiteOpenHelper 并完成 创建 更新 功能

Java代码
public class DBHelper extends SQLiteOpenHelper {

public static final String TB_NAME = "mycountry";
public static final String ID = "_id";
public static final String COUNTRY = "country";
public static final String CODE = "code";


public DBHelper(Context context, String name,
CursorFactory factory,int version) {
super(context, name, factory, version);
}

public void onCreate(SQLiteDatabase db) {

db.execSQL("CREATE TABLE IF NOT EXISTS "
+ TB_NAME + " ("
+ ID + " INTEGER PRIMARY KEY,"
+ COUNTRY + " VARCHAR,"
+ CODE + " INTEGER)");
}

public void onUpgrade(SQLiteDatabase db,
int oldVersion, int newVersion) {

db.execSQL("DROP TABLE IF EXISTS "+TB_NAME);
onCreate(db);
}
}

public class DBHelper extends SQLiteOpenHelper {

public static final String TB_NAME = "mycountry";
public static final String ID = "_id";
public static final String COUNTRY = "country";
public static final String CODE = "code";


public DBHelper(Context context, String name,
CursorFactory factory,int version) {
super(context, name, factory, version);
}

public void onCreate(SQLiteDatabase db) {

db.execSQL("CREATE TABLE IF NOT EXISTS "
+ TB_NAME + " ("
+ ID + " INTEGER PRIMARY KEY,"
+ COUNTRY + " VARCHAR,"
+ CODE + " INTEGER)");
}

public void onUpgrade(SQLiteDatabase db,
int oldVersion, int newVersion) {

db.execSQL("DROP TABLE IF EXISTS "+TB_NAME);
onCreate(db);
}
}







2. 从SQLiteOpenHelper 得到SQLiteDatabase的实例

Java代码
DBHelper helper = new DBHelper(this, DB_NAME, null, VERSION);

SQLiteDatabase db = helper.getWritableDatabase();

DBHelper helper = new DBHelper(this, DB_NAME, null, VERSION);

SQLiteDatabase db = helper.getWritableDatabase();





3. SQLiteDatabase 的一些操作：

* 插入数据：

Java代码
ContentValues values = new ContentValues();
values.put(DBHelper.COUNTRY, "中国");
values.put(DBHelper.CODE, 86);
db.insert(DBHelper.TB_NAME,DBHelper.ID, values);

ContentValues values = new ContentValues();
values.put(DBHelper.COUNTRY, "中国");
values.put(DBHelper.CODE, 86);
db.insert(DBHelper.TB_NAME,DBHelper.ID, values);



* 改动数据

Java代码
db.insert(DBHelper.TB_NAME,DBHelper.ID,null);
values.clear();
values.put(DBHelper.COUNTRY, "意大利");
values.put(DBHelper.CODE, 39);
db.update(DBHelper.TB_NAME, values,DBHelper.ID + " = 2",null);

db.insert(DBHelper.TB_NAME,DBHelper.ID,null);
values.clear();
values.put(DBHelper.COUNTRY, "意大利");
values.put(DBHelper.CODE, 39);
db.update(DBHelper.TB_NAME, values,DBHelper.ID + " = 2",null);

* execSQL 执行SQL语言

Java代码
db.execSQL("INSERT INTO "
+ DBHelper.TB_NAME + "("
+ DBHelper.COUNTRY + ","
+ DBHelper.CODE + ") VALUES "
+ "('洪都拉斯',504)");

db.execSQL("INSERT INTO "
+ DBHelper.TB_NAME + "("
+ DBHelper.COUNTRY + ","
+ DBHelper.CODE + ") VALUES "
+ "('洪都拉斯',504)");

* 查询数据

Java代码
Cursor c = db.query(DBHelper.TB_NAME,null,null,null,null,null,
DBHelper.CODE+" DESC");

Cursor c = db.query(DBHelper.TB_NAME,null,null,null,null,null,
DBHelper.CODE+" DESC");

* 删除数据所有数据

Java代码
db.delete(DBHelper.TB_NAME,null,null);

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