如何向sqlite添加新表？答案

【问题标题】：How to add new table to sqlite?如何向sqlite添加新表？
【发布时间】：2019-05-22 03:03:02
【问题描述】：

我需要为我现有的表添加一个新的列名id INTEGER AUTOINCREMENT 和一个用于当前数据库的新表。如何使用“升级”？是否需要更改版本号？

initDb() async {
    io.Directory documentsDirectory = await getApplicationDocumentsDirectory();
    String path = join(documentsDirectory.path, "HelperDatabase.db");
    var theDb = await openDatabase(path, version: 1, onCreate: _onCreate, onUpgrade: _onUpgrade);
    return theDb;
  }

如何使用_onUpgrade

void _onUpgrade(Database db, int oldVersion, int newVersion)async{

  }

也需要加列吗？

void _onCreate(Database db, int version) async {

    await db.execute(
        """CREATE TABLE AssetAssemblyTable(e INTEGER, a INTEGER, c INTEGER)""");

【问题讨论】：

标签： dart flutter sqflite

【解决方案1】：

要从旧版本更新您的数据库，您应该将version 更改为2。您应该更改 onCreate 和 onUpdate，如下所示。

// This is called for new users who have no old db
void _onCreate(Database db, int version) async {

  // if `AssetAssemblyTable` has a new column in version 2, add the column here.
  await db.execute(
    """CREATE TABLE AssetAssemblyTable(e INTEGER, a INTEGER, c INTEGER)""");
  )
  await db.execute("CREATE TABLE NewTable...") // create new Table
}

// This is called for existing users who have old db(version 1) 
void _onUpgrade(Database db, int oldVersion, int newVersion)async{
  // In this case, oldVersion is 1, newVersion is 2
  if (oldVersion == 1) {
      await db.execute("ALTER TABLE AssetAssemblyTable...") // add new column to existing table.
      await db.execute("CREATE TABLE NewTable...") // create new Table
  }
}

【讨论】：

Alter table是否需要增加_onCreate()方法版本号？
您不必对_onCreate 中的version 变量做任何事情。我猜这是为了调试目的。
错误信息：Unhandled Exception: DatabaseException(table UsernameTable has no column named rememberMe (Sqlite code 1): , while compiling: INSERT OR REPLACE INTO UsernameTable (username, rememberMe) VALUES (?, ?), (OS error - 2:No such file or directory)) sql 'INSERT OR REPLACE INTO UsernameTable (username, rememberMe) VALUES (?, ?)' args [term@melfs, 1]}
initDb() async { io.Directory documentsDirectory = await getApplicationDocumentsDirectory(); String path = join(documentsDirectory.path, "HelperDatabase.db"); var theDb = await openDatabase(path, version: 4, onCreate: _onCreate, onUpgrade: _onUpgrade); return theDb; }
void _onUpgrade(Database db, int oldVersion, int newVersion)async{ if(oldVersion != 5){ await db.execute("ALTER TABLE UsernameTable ADD COLUMN rememberMe INTEGER DEFAULT 0"); } }