Android学习（27） -- 数据存储之SQLite数据库的增删改查

数据库的增删改查

SQL语句

• insert into person (name, phone, money) values (‘张三’, ‘159874611’, 2000);
• delete from person where name = ‘李四’ and _id = 4;
• update person set money = 6000 where name = ‘李四’;
• select name, phone from person where name = ‘张三’;

执行SQL语句实现增删改查

    //插入
    db.execSQL("insert into person (name, phone, money) 
    values (?, ?, ?);", new Object[]{"张三", 15987461, 75000});
    //查找
    Cursor cs = db.rawQuery("select _id, name, money 
    from person where name = ?;", new String[]{"张三"});

* 测试方法执行前会调用此方法

    protected void setUp() throws Exception {
        super.setUp();
        //                  获取虚拟上下文对象
        oh = new MyOpenHelper(getContext(), "people.db", null, 1);
    }

使用api实现增删改查

• 插入

  //以键值对的形式保存要存入数据库的数据
  ContentValues cv = new ContentValues();
  cv.put("name", "刘能");
  cv.put("phone", 1651646);
  cv.put("money", 3500);
  //返回值是改行的主键，如果出错返回-1
  long i = db.insert("person", null, cv);
  

• 删除

  //返回值是删除的行数
  int i = db.delete("person", "_id = ? and name = ?", new String[]{"1", "张三"});
  

• 修改

  ContentValues cv = new ContentValues();
  cv.put("money", 25000);
  int i = db.update("person", cv, "name = ?", new String[]{"赵四"});
  

• 查询

  //arg1:要查询的字段
  //arg2：查询条件
  //arg3:填充查询条件的占位符
  Cursor cs = db.query("person", new String[]{"name", 
  "money"}, "name = ?", new String[]{"张三"}, null, null, null);
  while(cs.moveToNext()){
      //                          获取指定列的索引值
      String name = cs.getString(cs.getColumnIndex("name"));
      String money = cs.getString(cs.getColumnIndex("money"));
      System.out.println(name + ";" + money);
  }
  

事务

• 保证多条SQL语句要么同时成功，要么同时失败
• 最常见案例：银行转账

• 事务api

  try {
      //开启事务
      db.beginTransaction();
      ...........
      //设置事务执行成功
      db.setTransactionSuccessful();
  } finally{
      //关闭事务
      //如果此时已经设置事务执行成功，则sql语句生效，否则不生效
      db.endTransaction();
  }
  

代码

    public class TestCase extends AndroidTestCase {

        //此时测试框架还没有初始化完毕，没有虚拟上下文对象
    //  private MyOpenHelper oh = new MyOpenHelper(getContext(), "people.db", null, 1);
        private MyOpenHelper oh;
        private SQLiteDatabase db;


        //测试框架初始化完毕之后，在测试方法执行之前，此方法调用
        @Override
        protected void setUp() throws Exception {
            super.setUp();

            oh = new MyOpenHelper(getContext(), "people.db", null, 1);
            db = oh.getWritableDatabase();
        }

        //测试方法执行完毕之后，此方法调用
        @Override
        protected void tearDown() throws Exception {
            // TODO Auto-generated method stub
            super.tearDown();
            db.close();
        }

        public void insert(){

    //      db.execSQL("insert into person (name, salary, phone)values(?, ?, ?)", 
            new Object[]{"老婆[1]", "13000", 138438});
    //      db.execSQL("insert into person (name, salary, phone)values(?, ?, ?)", 
            new Object[]{"儿子", 14000, "13888"});
            db.execSQL("insert into person (name, salary, phone)values(?, ?, ?)", 
                new Object[]{"小小", 14000, "13888"});
            }

        public void delete(){
            db.execSQL("delete from person where name = ?", new Object[]{"小小"});
        }

        public void update(){
            db.execSQL("update person set phone = ? where name = ?", new Object[]{186666, "儿子"});
        }

        public void select(){
            Cursor cursor = db.rawQuery("select name, salary from person", null);

            while(cursor.moveToNext()){
                //通过列索引获取列的值
                String name = cursor.getString(cursor.getColumnIndex("name"));
                String salary = cursor.getString(1);
                System.out.println(name + ";" + salary);
            }
        }

        public void insertApi(){
            //把要插入的数据全部封装至ContentValues对象
            ContentValues values = new ContentValues();
            values.put("name", "小龙");
            values.put("phone", "15999");
            values.put("salary", 16000);
            db.insert("person", null, values);
        }

        public void deleteApi(){
            int i = db.delete("person", "name = ? and _id = ?", new String[]{"儿子", "3"});
            System.out.println(i);
        }

        public void updateApi(){
            ContentValues values = new ContentValues();
            values.put("salary", 26000);
            int i = db.update("person", values, "name = ?", new String[]{"小龙"});
            System.out.println(i);
        }

        public void selectApi(){
            Cursor cursor = db.query("person", null, null, null, null, null, null, null);
            while(cursor.moveToNext()){
                String name = cursor.getString(cursor.getColumnIndex("name"));
                String phone = cursor.getString(cursor.getColumnIndex("phone"));
                String salary = cursor.getString(cursor.getColumnIndex("salary"));
                System.out.println(name + ";" + phone + ";" + salary);
            }
        }

        public void transaction(){
            try{
                //开启事务
                db.beginTransaction();
                ContentValues values = new ContentValues();
                values.put("salary", 12000);
                db.update("person", values, "name = ?", new String[]{"小志"});

                //清空
                values.clear();

                values.put("salary", 16000);
                db.update("person", values, "name = ?", new String[]{"小志的儿子"});

                //int i = 3/0;
                //设置  事务执行成功
                db.setTransactionSuccessful();
            }
            finally{
                //关闭事务，同时提交，如果已经设置事务执行成功，那么sql语句就生效了，反之，sql语句回滚
                db.endTransaction();
            }
        }
    }