andriod sqlite 详解转载

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "mydata.db"; //数据库名称

    private static final int version = 1; //数据库版本

    public DatabaseHelper(Context context) {

        super(context, DB_NAME, null, version);

        // TODO Auto-generated constructor stub

    }

    @Override

    public void onCreate(SQLiteDatabase db) {

        String sql = "create table user(username varchar(20) not null , password varchar(60) not null );";         

        db.execSQL(sql);

    }

    @Override

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

        // TODO Auto-generated method stub

    }

}

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DatabaseHelper database = new DatabaseHelper(this);//这段代码放到Activity类中才用this

SQLiteDatabase db = null;

db = database.getReadalbeDatabase();

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ContentValues cv = new ContentValues();//实例化一个ContentValues用来装载待插入的数据cv.put("username","Jack Johnson");//添加用户名

cv.put("password","iLovePopMusic"); //添加密码

db.insert("user",null,cv);//执行插入操作

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String sql = "insert into user(username,password) values (‘Jack Johnson‘,‘iLovePopMuisc‘);//插入操作的SQL语句

db.execSQL(sql);//执行SQL语句

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String whereClause = "username=?";//删除的条件

String[] whereArgs = {"Jack Johnson"};//删除的条件参数

db.delete("user",whereClause,whereArgs);//执行删除

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String sql = "delete from user where username=‘Jack Johnson‘";//删除操作的SQL语句

db.execSQL(sql);//执行删除操作

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ContentValues cv = new ContentValues();//实例化ContentValues

cv.put("password","iHatePopMusic");//添加要更改的字段及内容

String whereClause = "username=?";//修改条件

String[] whereArgs = {"Jack Johnson"};//修改条件的参数

db.update("user",cv,whereClause,whereArgs);//执行修改

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String sql = "update [user] set password = ‘iHatePopMusic‘ where username=‘Jack Johnson‘";//修改的SQL语句

db.execSQL(sql);//执行修改

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Cursor c = db.query("user",null,null,null,null,null,null);//查询并获得游标

if(c.moveToFirst()){//判断游标是否为空

    for(int i=0;i<c.getCount();i++){

        c.move(i);//移动到指定记录

        String username = c.getString(c.getColumnIndex("username");

        String password = c.getString(c.getColumnIndex("password"));

    }

}

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Cursor c = db.rawQuery("select * from user where username=?",new Stirng[]{"Jack Johnson"});

if(cursor.moveToFirst()) {

    String password = c.getString(c.getColumnIndex("password"));

}