SQLite在模拟器6.0不能创建表

发布网友发布时间：2022-04-07 18:19

共2个回答

懂视网时间：2022-04-07 22:40

package com.example.sqliteopenhelper; 2 3 import android.content.Context; 4 import android.database.sqlite.SQLiteDatabase; 5 import android.database.sqlite.SQLiteDatabase.CursorFactory; 6 import android.database.sqlite.SQLiteOpenHelper; 7 import android.util.Log; 8 9 public class MydbOpenHelper extends SQLiteOpenHelper{ 10 11 public MydbOpenHelper(Context context, String name, CursorFactory factory, int version){ 12 super(context, name, factory, version); 13 } 14 15 @Override 16 public void onCreate(SQLiteDatabase db) { 17 String createtable = "create table user(id int, name varchar(20), password char(8))"; 18 db.execSQL(createtable); 19 System.out.println("MydbOpenHelper.onCreate()"); 20 21 } 22 23 @Override 24 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 25 Log.i("MydbOpenHelper","oldVersion" + oldVersion + "newVersion" + newVersion); 26 System.out.println("MydbOpenHelper.onUpgrade()"); 27 28 } 29 } MydbOpenHelper

 1 package com.example.sqliteopenhelper;
 2 
 3 import android.app.Activity;
 4 import android.content.ContentValues;
 5 import android.database.Cursor;
 6 import android.database.sqlite.SQLiteDatabase;
 7 import android.os.Bundle;
 8 import android.util.Log;
 9 import android.view.Menu;
10 import android.view.MenuItem;
11 import android.view.View;
12 
13 public class MainActivity extends Activity {
14 SQLiteDatabase db = null;
15 
16  @Override
17 protected void onCreate(Bundle savedInstanceState) {
18  super.onCreate(savedInstanceState);
19  setContentView(R.layout.activity_main);
20  
21  MydbOpenHelper dbhelper = new MydbOpenHelper(this, "userinfo.db", null, 1);
22  db = dbhelper.getWritableDatabase();
23 
24  }
25 
26 public void insert(View v){
27  ContentValues c = new ContentValues();
28  //c.put("id", 2);
29  //c.put("name", "user222");
30  //c.put("password", "222");
31  
32  c.put("id", 1);
33  c.put("name", "user1");
34  c.put("password", "222");
35  
36  db.insert("user", null, c);
37  }
38 public void delete(View v){
39  db.delete("user", "id=? and name=?", new String[]{"1","user1"});
40  }
41 public void update(View v){
42  ContentValues c = new ContentValues();
43  c.put("name", "user222");
44  c.put("password", "88888888");
45  db.update("user", c, "id=?", new String[]{"2"});
46  }
47 public void query(View v){
48  String[] colums = {"id", "name", "password"};
49  Cursor c = db.query("user", colums, null, null, null, null, null);
50  
51  while(c.moveToNext()){
52  int id = c.getInt(c.getColumnIndex("id"));
53  String username = c.getString(c.getColumnIndex("name"));
54  String password = c.getString(c.getColumnIndex("password"));
55  Log.i("sqliteopenhelper", id + "," +username+"," +password);
56  }
57  }
58 }

MainActivity.java

006_02SQLite_OpenHelper

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热心网友时间：2022-04-07 19:48

不仅是sqlite创建表不能以数字开头，绝大多数的数据库都不允许用数字开头。这是因为各数据库的开发规范要求，并无其他原因。
　　数据表：
　　数据表是数据库中一个非常重要的对象，是其他对象的基础。根据信息的分类情况，一个数据库中可能包含若干个数据表。
　　建表原则：
　　为减少数据输入错误，并能使数据库高效工作，表设计应按照一定原则对信息进行分类，同时为确保表结构设计的合理性，通常还要对表进行规范化设计，以消除表中存在的冗余，保证一个表只围绕一个主题，并使表容易维护。