ejemplo de código de tutorial de flutter sqlite

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Ejemplo 1: eliminar consulta en sqlite flutter

// Get a location using getDatabasesPath
var databasesPath = await getDatabasesPath();
String path =join(databasesPath,'demo.db');// Delete the database
await deleteDatabase(path);// open the databaseDatabasedatabase= await openDatabase(path, version: 1,
    onCreate: (Database db,int version) async 
  // When creating the db, create the table
  await db.execute('CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)');
);// Insert some records in a transaction
await database.transaction((txn) async 
  int id1 = await txn.rawInsert('INSERT INTO Test(name, value, num) VALUES("some name", 1234, 456.789)');print('inserted1: $id1');int id2 = await txn.rawInsert('INSERT INTO Test(name, value, num) VALUES(?, ?, ?)',['another name',12345678,3.1416]);print('inserted2: $id2');
);// Update some recordint count = await database.rawUpdate('UPDATE Test SET name = ?, value = ? WHERE name = ?',['updated name','9876','some name']);print('updated: $count');// Get the records
List<Map> list = await database.rawQuery('SELECT * FROM Test');
List<Map> expectedList =[
  'name': 'updated name','id': 1,'value': 9876,'num': 456.789,
  'name': 'another name','id': 2,'value': 12345678,'num': 3.1416
];print(list);print(expectedList);
assert(const DeepCollectionEquality().equals(list, expectedList));// Count the records
count = Sqflite
    .firstIntValue(await database.rawQuery('SELECT COUNT(*) FROM Test'));
assert(count ==2);// Delete a record
count = await database.rawDelete('DELETE FROM Test WHERE name = ?',['another name']);
assert(count ==1);// Close the database
await database.close();

Ejemplo 2: sqlite en flutter

import'dart:async';import'dart:io';import'package:path/path.dart';import'package:path_provider/path_provider.dart';import'package:sqflite/sqflite.dart';import'Product.dart'; 

class SQLiteDbProvider 
   SQLiteDbProvider._(); 
   static final SQLiteDbProvider db = SQLiteDbProvider._(); 
   static Database _database; 
   
   Future<Database> get database async 
      if(_database !=null)return _database; 
      _database = await initDB();return _database; 
    
   initDB() async 
      Directory documentsDirectory = await 
      getApplicationDocumentsDirectory(); 
      String path =join(documentsDirectory.path,"ProductDB.db");return await openDatabase(
         path, version: 1, 
         onOpen: (db) , 
         onCreate: (Database db,int version) async 
            await db.execute("CREATE TABLE Product (""id INTEGER PRIMARY KEY,""name TEXT,""description TEXT,""price INTEGER,""image TEXT"")"); 
            await db.execute("INSERT INTO Product ('id', 'name', 'description', 'price', 'image') 
               values (?, ?, ?, ?, ?)",[1,"iPhone","iPhone is the stylist phone ever",1000,"iphone.png"]); 
            await db.execute("INSERT INTO Product ('id', 'name', 'description', 'price', 'image') 
               values (?, ?, ?, ?, ?)",[2,"Pixel","Pixel is the most feature phone ever",800,"pixel.png"]);
            await db.execute("INSERT INTO Product ('id', 'name', 'description', 'price', 'image') 
               values (?, ?, ?, ?, ?)",[3,"Laptop","Laptop is most productive development tool",2000,"laptop.png"]); 
            await db.execute("INSERT INTO Product ('id', 'name', 'description', 'price', 'image') 
               values (?, ?, ?, ?, ?)",[4,"Tablet","Laptop is most productive development tool",1500,"tablet.png"]); 
            await db.execute("INSERT INTO Product ('id', 'name', 'description', 'price', 'image') 
               values (?, ?, ?, ?, ?)",[5,"Pendrive","Pendrive is useful storage medium",100,"pendrive.png"]);
            await db.execute("INSERT INTO Product ('id', 'name', 'description', 'price', 'image') 
               values (?, ?, ?, ?, ?)",[6,"Floppy Drive","Floppy drive is useful rescue storage medium",20,"floppy.png"]); 
         
      ); 
   
   Future<List<Product>> getAllProducts() async 
      final db = await database; 
      List<Map> results = await db.query("Product",columns: Product.columns, orderBy: "id ASC"); 
      List<Product> products = new List();   
      results.forEach((result) 
         Product product = Product.fromMap(result); 
         products.add(product); 
      );return products; 
    
   Future<Product> getProductById(int id) async 
      final db = await database; 
      var result = await db.query("Product",where: "id = ", whereArgs: [id]);return result.isNotEmpty ? Product.fromMap(result.first) : Null; 
    
   insert(Product product) async  
      final db = await database; 
      var maxIdResult = await db.rawQuery("SELECT MAX(id)+1 as last_inserted_id FROM Product"); 
      var id = maxIdResult.first["last_inserted_id"]; 
      var result = await db.rawInsert("INSERT Into Product (id, name, description, price, image)"" VALUES (?, ?, ?, ?, ?)",[id, product.name, product.description, product.price, product.image]);return result; 
    
   update(Product product) async  
      final db = await database; 
      var result = await db.update("Product", product.toMap(),where: "id = ?", whereArgs: [product.id]);return result; 
    
   delete(int id) async  
      final db = await database; 
      db.delete("Product",where: "id = ?", whereArgs: [id]);
    

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