一、使用SQldatabase
//默认情况下,每个程序都有一个数据库,本文介绍如何使用自己数据库
- 基础语句
- db.execSQL(sql) //执行任何SQL语句
- db.insert(table,nullColumnHack,values)
- db.delete(table,whereClause,whereArgs)
- db.update(table,values,whereClause,whereArgs)
- db.query(table,columns,selection,selectionArgs,groupBy,having,orderBy)
- db.rawQuery(sql,selectionArgs)
2.创建数据库并且打开
SQLiteDatabase db = openOrCreateDatabase("stu.db", MODE_PRIVATE, null); //(数据库名字;数据库权限;查询时游标实例化)
//创建表if表不存在
db.execSQL("create table if not exists stutb(_id integer primary key autoincrement,name text not null,sex text not null,age integer not null)");
3.插入数据
ContentValues values = new ContentValues();
values.put("name", "张三"); //("key",)
values.put("sex", "男");
values.put("age", 19);
db.insert("stutb", null, values);
- 第二种方法
- //向数据库中添加变量值
- db.exectSQL("insert into stutb (name,sex,age)values(?,?,?)",new Object[] {name1,sex1,age1});
- db.exectSQL("insert into stutb (name,sex,age)values('小明','女',23 )");
4.查询数据库
Cursor c=db.rawQuery("select * from stutb",null);
if(c!=null)
{
while(c.moveToNext())
{
Log.v("tag","_id:"+ c.getInt(0));
Log.v("tag","name:"+ c.getString(1));
Log.v("tag","sex:"+ c.getString(2));
Log.v("tag","age:"+ c.getInt(3));
}
c.close(); //释放游标
}
db.close(); //释放数据库
Cursor c = db.query("stutb", null, "_id>?", new String[]{"0"}, null, null, "name"); //查找所有字段,并按名字排序
if (c!=null) {
String [] columns= c.getColumnNames();
while (c.moveToNext()) {
for (String columnName : columns) {
Log.i("info", c.getString(c.getColumnIndex(columnName)));
}
}
c.close();
}
5.更改数据库值
values.clear();
values.put("sex", "女");
db.update("stutb", values, "_id>?", new String[]{"3"});//将全部id>3的人的性别改成女
6.删除数据库中值
db.delete("stutb", "name like ?", new String[]{"%丰%"});//删除所有名字中带有丰的人
7.游标Cursor介绍:游标接口,提供了便利查询结果的方法
常用方法:
- getCount() //总记录条数
- isFirst() //判断是否是第一条记录
- isLast() //判断是否是最后一条记录
- moveToFirst() //移动到第一条记录
- moveToLast() //移动到最后一条记录
move(int offset) //移动到指定目录 - moveToNext() //移动到下一条记录
- moveToPrevious() //移动到上一条记录
- getColumnIndexOrThrow(String columnName) //据列名称获取列索引
- getInt(int columnIndex) //获取指定列索引的int类型值
- getString(int columnIndex) //获取指定列缩影的String类型值
二、使用SQLDBhelper
DBOpenhelper.java
package com.imooc.sqlitedemo3;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DBOpenHelper extends SQLiteOpenHelper{
public DBOpenHelper(Context context, String name) {
super(context, name, null, 1);
// TODO Auto-generated constructor stub
}
public DBOpenHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
@Override//首次创建数据库的时候调用 一般可以把建库 建表的操作
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("create table if not exists stutb(_id integer primary key autoincrement,name text not null,sex text not null,age integer not null)");
db.execSQL("insert into stutb(name,sex,age)values('张三','女',18)");
}
@Override//当数据库的版本发生变化的时候 会自动执行
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
MainActivity.java
package com.imooc.sqlitedemo3;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DBOpenHelper helper = new DBOpenHelper(MainActivity.this, "stu.db");
// helper.getReadableDatabase();//获取一个只读的数据库 只能查询 不能写入 不能更新
SQLiteDatabase db = helper.getWritableDatabase();
// db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy)
Cursor c = db.rawQuery("select * from stutb", null);
if (c!=null) {
String [] cols = c.getColumnNames();
while (c.moveToNext()) {
for (String ColumnName : cols) {
Log.i("info", ColumnName+":"+c.getString(c.getColumnIndex(ColumnName)));
}
}
c.close();
}
db.close();
}
}