Android学习（27） -- 数据存储之SQLite数据库的增删改查

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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-1long 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();            }        }    }

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