SQLiteDatabase 数据库使用

0 SQLiteDatabases数据库特点

一种切入式关系型数据库，支持事务，可使用SQL语言，独立，无需服务。程序内通过类名可访问数据库，程序外不可以访问。

SQLiteDatabases数据库使用方法

1 创建数据库及表，使用 SQLiteOpenHelper 类

public class DBHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "zc.db";//数据库名称
    public static final String TANLE_NAME = "car";//表名
    private static final int DATABASE_VERSION = 1;//数据库版本

    public DBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    //数据库第一次被创建时执行此方法，创建表
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table if not exists" + TANLE_NAME +
                "(_id integer primary key autoincrement ,brandName varchar ,brandId integer ,logo text)");
    }

    //如果DATABASE_VERSION改为2，系统发现现有数据库版本不同,即会调用onUpgrade
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("ALTER TABLE" + TANLE_NAME + " ADD COLUMN other text");
    }

}

2 操作SQLite数据库表，使用SQLiteDatabase类

SQLiteDatabase 增删改查方法

第一种：execSQL() , rawQuery() ,要求sql语法熟练

第二张：insert()，update()，deleter()，query()

public class DBManager {

    private final DBHelper dbHelper;//DBHelper对象
    private final SQLiteDatabase db;//SQLiteDatabase对象

    public DBManager(Context context) {
        dbHelper = new DBHelper(context);
        db = dbHelper.getWritableDatabase();//真正创建或打开数据库，获取可读写SQLiteDatabase对象
    }

    //添加车辆列表
    public void addCarList(List<Car> carList) {
        db.beginTransaction();
        try {
            for (Car car : carList) {
                add(car);
            }
            db.setTransactionSuccessful();
        } finally {
            db.endTransaction();
        }
    }

    //新增
    public void add(Car car) {
        ContentValues cv = new ContentValues();
        cv.put("brandId", car.getBrandId());
        cv.put("brandName", car.getBrandName());
        cv.put("logo", car.getLogo());
        //rowid 返回新添记录的行号，与主键id无关
        long rowid = db.insert(DBHelper.TANLE_NAME, null, cv);
        db.close();
    }

    //删除
    public void delete(String brandId) {
        db.delete(DBHelper.TANLE_NAME, "brandId = ? ", new String[]{brandId});
        db.close();
    }

    //修改
    public void update(Car car) {
        ContentValues cv = new ContentValues();
        cv.put("brandName", car.getBrandName());
        db.update(DBHelper.TANLE_NAME, cv, "brandId = ? ", new String[]{car.getBrandId()});
        db.close();
    }

    //查询
    public List<Car> queryList() {
        List<Car> list = new ArrayList<>();
        Cursor cursor = db.rawQuery("select * from " + DBHelper.TANLE_NAME, null);
        while (cursor.moveToNext()) {
            Car car = new Car();
            car.setBrandId(cursor.getString(cursor.getColumnIndex("brandId")));
            car.setBrandName(cursor.getString(cursor.getColumnIndex("brandName")));
            car.setLogo(cursor.getString(cursor.getColumnIndex("logo")));
            list.add(car);
        }
        cursor.close();
        db.close();
        return list;
    }

    public Car queryCar(String brandId) {
        Car car = new Car();
        Cursor cursor = db.rawQuery("select * from " + DBHelper.TANLE_NAME + " where brandId = ? ", new String[]{brandId});
        while (cursor.moveToNext()) {
            car.setBrandId(cursor.getString(cursor.getColumnIndex("brandId")));
            car.setBrandName(cursor.getString(cursor.getColumnIndex("brandName")));
            car.setLogo(cursor.getString(cursor.getColumnIndex("logo")));
        }
        cursor.close();
        db.close();
        return car;
    }

}