关于数据库的复习
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SQLiteDatabase的rawQuery()用于执行select语句
第一种
package com.example.admin.xmltest678;import java.util.ArrayList;import java.util.List;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;public class PersonService { private DBOpenHelper dbOpenHelper; public PersonService(Context context) { this.dbOpenHelper = new DBOpenHelper(context); } public void payment(){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.beginTransaction();//开启事务 try{ db.execSQL("update person set amount=amount-10 where personid=1"); db.execSQL("update person set amount=amount+10 where personid=2"); db.setTransactionSuccessful();//设置事务的标志为True }finally{ db.endTransaction();//结束事务,有两种情况:commit,rollback, //事务的提交或回滚是由事务的标志决定的,如果事务的标志为True,事务就会提交,否侧回滚,默认情况下事务的标志为False } } /** * 添加记录 * @param person */ public void save(Person person){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.execSQL("insert into person(name, phone, amount) values(?,?,?)", new Object[]{person.getName(), person.getPhone(), person.getAmount()}); } /** * 删除记录 * @param id 记录ID */ public void delete(Integer id){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.execSQL("delete from person where personid=?", new Object[]{id}); } /** * 更新记录 * @param person */ public void update(Person person){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.execSQL("update person set name=?,phone=?,amount=? where personid=?", new Object[]{person.getName(), person.getPhone(), person.getAmount(), person.getId()}); } /** * 查询记录 * @param id 记录ID * @return */ public Person find(Integer id){ SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.rawQuery("select * from person where personid=?", new String[]{id.toString()}); if(cursor.moveToFirst()){ int personid = cursor.getInt(cursor.getColumnIndex("personid")); int amount = cursor.getInt(cursor.getColumnIndex("amount")); String name = cursor.getString(cursor.getColumnIndex("name")); String phone = cursor.getString(cursor.getColumnIndex("phone")); return new Person(personid, name, phone, amount); } cursor.close(); return null; } /** * 分页获取记录 * @param offset 跳过前面多少条记录 * @param maxResult 每页获取多少条记录 * @return */ public List<Person> getScrollData(int offset, int maxResult){ List<Person> persons = new ArrayList<Person>(); SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.rawQuery("select * from person order by personid asc limit ?,?", new String[]{String.valueOf(offset), String.valueOf(maxResult)}); while(cursor.moveToNext()){ int personid = cursor.getInt(cursor.getColumnIndex("personid")); int amount = cursor.getInt(cursor.getColumnIndex("amount")); String name = cursor.getString(cursor.getColumnIndex("name")); String phone = cursor.getString(cursor.getColumnIndex("phone")); persons.add(new Person(personid, name, phone, amount)); } cursor.close(); return persons; } /** * 分页获取记录 * @param offset 跳过前面多少条记录 * @param maxResult 每页获取多少条记录 * @return */ public Cursor getCursorScrollData(int offset, int maxResult){ SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.rawQuery("select personid as _id,name,phone,amount from person order by personid asc limit ?,?", new String[]{String.valueOf(offset), String.valueOf(maxResult)}); return cursor; } /** * 获取记录总数 * @return */ public long getCount(){ SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.rawQuery("select count(*) from person", null); cursor.moveToFirst(); long result = cursor.getLong(0); cursor.close(); return result; }}
第二种
package com.example.admin.xmltest678;import java.util.ArrayList;import java.util.List;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;public class PersonService { private DBOpenHelper dbOpenHelper; public PersonService(Context context) { this.dbOpenHelper = new DBOpenHelper(context); } /** * 添加记录 * @param person */ public void save(Person person){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("name", person.getName()); values.put("phone", person.getPhone()); values.put("amount", person.getAmount()); db.insert("person", null, values); } /** * 删除记录 * @param id 记录ID */ public void delete(Integer id){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.delete("person", "personid=?", new String[]{id.toString()}); } /** * 更新记录 * @param person */ public void update(Person person){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("name", person.getName()); values.put("phone", person.getPhone()); values.put("amount", person.getAmount()); db.update("person", values, "personid=?", new String[]{person.getId().toString()}); } /** * 查询记录 * @param id 记录ID * @return */ public Person find(Integer id){ SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.query("person", null, "personid=?", new String[]{id.toString()}, null, null, null); if(cursor.moveToFirst()){ int personid = cursor.getInt(cursor.getColumnIndex("personid")); int amount = cursor.getInt(cursor.getColumnIndex("amount")); String name = cursor.getString(cursor.getColumnIndex("name")); String phone = cursor.getString(cursor.getColumnIndex("phone")); return new Person(personid, name, phone, amount); } cursor.close(); return null; } /** * 分页获取记录 * @param offset 跳过前面多少条记录 * @param maxResult 每页获取多少条记录 * @return */ public List<Person> getScrollData(int offset, int maxResult){ List<Person> persons = new ArrayList<Person>(); SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.query("person", null, null, null, null, null, "personid asc", offset+ ","+ maxResult); while(cursor.moveToNext()){ int personid = cursor.getInt(cursor.getColumnIndex("personid")); int amount = cursor.getInt(cursor.getColumnIndex("amount")); String name = cursor.getString(cursor.getColumnIndex("name")); String phone = cursor.getString(cursor.getColumnIndex("phone")); persons.add(new Person(personid, name, phone, amount)); } cursor.close(); return persons; } /** * 获取记录总数 * @return */ public long getCount(){ SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.query("person", new String[]{"count(*)"}, null, null, null, null, null); cursor.moveToFirst(); long result = cursor.getLong(0); cursor.close(); return result; }}
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