数据存储之SQLiteDatabase

SQLiteDatabase: 轻量级的关系数据库

特点：轻量级、独立性、隔离性、跨平台、多语言接口、安全

利用命令行操作：

ls:可显示下面的全部内容

adb shell

ls

cd data

cd data

cd 包名

cd database

可以看见

database.db

用sqlite3 database.db 进入数据库

sql语句就可以增删改查

一： 直接对现有的数据库

SQLiteDatabase db = openOrCreateDatabase("database.db",MODE_PRIVATE,null);

db.execSQL("create table TABLENAME (COLUMNNAME varchar(20),.....)");

二。继承SQLiteOpenHelper 重写onCreate（初始化执行，只执行一次） 和 onUpgrade(Version 发生改变时执行)方法

使用：

<span style="font-family: Arial, Helvetica, sans-serif;">MyDBHelper  helper = </span><span style="font-family: Arial, Helvetica, sans-serif;">MyDBHelper .getInstance(getContext());</span>

<span style="font-family: Arial, Helvetica, sans-serif;">SQLiteDatabase db = helper.getWritableDatabase();//写入方式打开，若磁盘已满会报错</span>

=helper.getReadableDatabase(); //先以写入方式得到，若磁盘满，就以只读方式打开

db.execSQL("SQL语句");

安卓的方式对数据库进行增删改查

db.query()/db.insert()/db.update()/db.delete();

Cursor cursor = db.query("tableName",null,null,nul.....);

返回的是游标Cursor

if (<span style="font-size:14px;">cursor </span>!= null && <span style="font-size:14px;">cursor</span>.getCount() > 0) {

<span style="white-space:pre">	</span>while (<span style="font-size:14px;">cursor</span>.moveToNext()) {
<span style="white-space:pre">	</span>String name = <span style="font-size:14px;">cursor</span>.getString(<span style="font-size:14px;">cursor</span>.getColumnIndex("columnname"));
<span style="white-space:pre">	</span>String sex = <span style="font-size:14px;">cursor</span>.getString(<span style="font-size:14px;">cursor</span>.getColumnIndex("columnname"));
}
}

public class MyDBHelper extends SQLiteOpenHelper{
private static MyDBHelper sHelper;
public static final String DB_NAME = "student_database.db";

public  static MyDBHelper getInstance(Context context){
if (sHelper ==null) {
sHelper = new MyDBHelper(context);
}
return sHelper;
}

private MyDBHelper(Context context) {
super(context, DB_NAME, null, ColumnData.StudentTable.STUDENT_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table student ("+ColumnData.StudentTable.COLUMN_ID+" int,"+ColumnData.StudentTable.COLUMN_NAME+" varchar(20))");
}

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

}

}