sqlite数据库初步介绍和实现数据库表的增删改查

下面是免费的sqlite的工具及注册码，可以实现在windows下操作sqlite数据库

http://download.csdn.net/detail/itjavawfc/8098051

一些知识点：其实和平常用到的数据库没有多大区别。

1. 加载驱动.
2. 连接数据库.
3. 操作数据库.

创建表:
create table person(
_id integer primary key,
name varchar(20),
age integer
);

添加: insert into person(name,age) values('lisi',19);

删除: delete from person where _id = 1;

修改: update person set name = '李四' where name = '王五';

查询所有: select * from person;

查询单条: select * from person where name = 'zhangsan';

其中加载驱动和连接数据库通过得到数据库的对象即可完成：

创建数据库的过程，在一个类的构造方法中，该类继承了sqliteOpenHelper

/*
	 * 数据库的构造函数
	 * name:数据库名称
	 * factory    游标工程
	 * version    数据库版本号，不可以小于1
	 */
	public PersonsqliteOpenHelper(Context context) {
		super(context,"itheima28.db",null,1);
		// TODO Auto-generated constructor stub
	}

下面是一个创建数据库的工具类：在构造方法中实现创建数据库，在程序调用的时候，在onCreate方法中创建表

/*
 * 数据库帮助类，用于创建和管理数据库的
 */
public class PersonsqliteOpenHelper extends sqliteOpenHelper{
	/*
	 * 数据库的构造函数
	 * name:数据库名称
	 * factory    游标工程
	 * version    数据库版本号，不可以小于1
	 */
	public PersonsqliteOpenHelper(Context context) {
		super(context,1);
		// TODO Auto-generated constructor stub
	}
	/*
	 * 数据库第一次创建时回调此方法
	 * 初始化一些表
	 * (non-Javadoc)
	 * @see android.database.sqlite.sqliteOpenHelper#onCreate(android.database.sqlite.sqliteDatabase)
	 */
	@Override
	public void onCreate(sqliteDatabase db) {
		// TODO Auto-generated method stub
		//操作数据库
		String sql="create table person(_id integer primary key,name char(20),age integer);";
		db.execsql(sql);
		
	}

	/*
	 * 数据库版本号更新时回调此方法
	 * 删除表，更新表
	 * (non-Javadoc)
	 * @see android.database.sqlite.sqliteOpenHelper#onUpgrade(android.database.sqlite.sqliteDatabase,int,int)
	 */
	@Override
	public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
		// TODO Auto-generated method stub
		
	}

}

实现增删改查数据库表的DAO，非常简单：

package com.itheima28.sqlitedemo.dao;
import java.util.ArrayList;
import java.util.List;
import com.itheima28.sqlitedemo.db.PersonsqliteOpenHelper;
import com.itheima28.sqlitedemo.entities.Person;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.sqliteDatabase;
public class PersonDao {
	private PersonsqliteOpenHelper mOpenHelper; // 数据库的帮助对象
	public PersonDao(Context context) {
		mOpenHelper = new PersonsqliteOpenHelper(context);
	}
	/*
	 * 添加到person表一条数据
	 */
	public void insert(Person person) {
		sqliteDatabase db = mOpenHelper.getWritableDatabase();
		if (db.isOpen()) { // 判断数据库是否打开
			// 执行添加数据库操作
			// db.execsql("insert into person(name,19);");
			db.execsql("insert into person(name,age) values(?,?);",new Object[] { person.getName(),person.getAge() });
			db.close(); // 数据库关闭
		}

	}

	public void delete(int id) {
		// 获得可写的数据库对象
		sqliteDatabase db = mOpenHelper.getWritableDatabase();
		if (db.isOpen()) {
			db.execsql("delete from person where _id=?;",new Integer[] { id });
			db.close(); // 数据库关闭
		}
	}

	public void update(int id,String name) {
		sqliteDatabase db = mOpenHelper.getWritableDatabase();
		if (db.isOpen()) {
			if (db.isOpen()) {
				db.execsql("update person set name=? where _id=?;",new Object[] { name,id });

				db.close(); // 数据库关闭
			}
		}
	}

	public List<Person> queryAll() {
		sqliteDatabase db = mOpenHelper.getWritableDatabase();
		if (db.isOpen()) {
			Cursor cursor = db
					.rawQuery("select _id,name,age from person",null);
			List<Person> personList = new ArrayList();
			if (cursor != null && cursor.getCount() >= 0) {
				int id;
				int age;
				String name;

				while (cursor.moveToNext()) {
					id = cursor.getInt(0); // 取第零列的数据
					name = cursor.getString(1);
					age = cursor.getInt(2);
					personList.add(new Person(id,age));

				}
				db.close();
				return personList;
			}

			db.close();
		}
		return null;

	}

	public Person queryItem(int id) {
		sqliteDatabase db = mOpenHelper.getWritableDatabase();
		if (db.isOpen()) {
			Cursor cursor = db.rawQuery(
					"select _id,age from person where _id=?",new String[] { id + "" });
			if (cursor != null && cursor.moveToFirst()) {
				int _id = cursor.getInt(0);
				String name = cursor.getString(1);
				int age = cursor.getInt(2);
				db.close();
				return new Person(_id,age);
			}
			db.close();
		}
		return null;

	}

}

实体类：

package com.itheima28.sqlitedemo.entities;
public class Person {
	private int id;
	private String name;
	private int age;
	public Person(int id,String name,int age) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString() {
		return "Person [id=" + id + ",name=" + name + ",age=" + age + "]";
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
}

测试：

package com.itheima28.sqlitedemo.test;

import java.util.List;

import com.itheima28.sqlitedemo.dao.PersonDao;
import com.itheima28.sqlitedemo.db.PersonsqliteOpenHelper;
import com.itheima28.sqlitedemo.entities.Person;

import android.test.AndroidTestCase;
import android.util.Log;

public class TestCase extends AndroidTestCase {

	private static final String TAG = "TestCase";

	public void test(){
		//数据库什么时候创建
		PersonsqliteOpenHelper openHelper=new PersonsqliteOpenHelper(getContext());
		
		//第一次连接数据库是创建数据库文件,会执行onCreate方法
		openHelper.getReadableDatabase();
		
	}
	
	public void testInsert(){
		PersonDao dao=new PersonDao(getContext());
	    dao.insert(new Person(5,"冠希",8));
	    dao.insert(new Person(6,"姚明",11));
	    dao.insert(new Person(8,"国家",78));
	
	}
	
	public void testDelete(){
		PersonDao dao=new PersonDao(getContext());
        dao.delete(1);
	}
	
	public void testUpdate(){
		PersonDao dao=new PersonDao(getContext());
        dao.update(1,"凤姐");
	}
	
	
	public void testQueryAll(){
		PersonDao dao=new PersonDao(getContext());
        List<Person> personList=dao.queryAll();
        for(Person person:personList){
        	Log.i(TAG,person.toString());
        }
		
	}
	
	public void testQueryItem(){
		PersonDao dao=new PersonDao(getContext());
        Person person=dao.queryItem(1);
        Log.i(TAG,person.toString());
	}
}

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