安卓学习之SQLite

本文主要总结了SQLite增删改查的语句和方法

SQL语句

name,phone,money为表的三个字段（windows可下载SQLite Expert软件，可以适应SQLite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';

java代码使用SQL语句：

    //创建OpenHelper对象。getContext()获取虚拟的上下文。
    MyOpenHelper oh = new MyOpenHelper(getContext(), "person.db", null, 1);
    //获得数据库对象,如果数据库不存在，先创建数据库，后获得，如果存在，则直接获得
     SQLiteDatabase db = oh.getWritableDatabase();

public void insert(){
db.execSQL("insert into person (name, salary, phone)values(?, ?, ?)", new Object[]{"小志", 14000, "13888"});
}

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

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

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
  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);
      }
  }