我必须从我的 C# 程序访问其他开发人员的一些 MySql View 。

所以经过一些搜索我决定 Entity Framework ，并使用这个问题中提到的驱动程序:Using MySQL with Entity Framework (MySQL .NET Connector)。

现在，我正在尝试获取一个 View 的第一个元素:

myEntities.events.First();

然后，我得到一个异常(exception):

System.Data.EntityCommandExecutionException was unhandled
  Message=An error occurred while executing the command definition. See the inner exception for details.
  Source=System.Data.Entity
  StackTrace:
       at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)
       at System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context, ObjectParameterCollection parameterValues)
       at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
       at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator()
       at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)
       at System.Data.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__0[TResult](IEnumerable`1 sequence)
       at System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle[TResult](IEnumerable`1 query, Expression queryRoot)
       at System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute[S](Expression expression)
       at System.Linq.Queryable.First[TSource](IQueryable`1 source)
       at J4N.GroopleReports.ReportManager.DataImporter.GenerateEvent(GroopleEntities groopleEntities) in C:\Users\J4N\Dropbox\WorkSpaces\DotNET\GroopleReports\ReportManager\DataImporter.cs:line 35
       at J4N.GroopleReports.ReportManager.DataImporter.Import() in C:\Users\J4N\Dropbox\WorkSpaces\DotNET\GroopleReports\ReportManager\DataImporter.cs:line 17
       at ImportTest.Program.Main(String[] args) in C:\Users\J4N\Dropbox\WorkSpaces\DotNET\GroopleReports\ImportTest\Program.cs:line 15
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: MySql.Data.MySqlClient.MySqlException
       Message=Every derived table must have its own alias
       Source=MySql.Data
       ErrorCode=-2147467259
       Number=1248
       StackTrace:
            at MySql.Data.MySqlClient.MySqlStream.ReadPacket()
            at MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& affectedRow, Int32& insertedId)
            at MySql.Data.MySqlClient.Driver.GetResult(Int32 statementId, Int32& affectedRows, Int32& insertedId)
            at MySql.Data.MySqlClient.Driver.NextResult(Int32 statementId, Boolean force)
            at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
            at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
            at MySql.Data.Entity.EFMySqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
            at System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior)
            at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)
       InnerException: 

我搜索了这个错误“Every derived table must have its own alias”是什么错误以及如何解决它，我在网上找到了一些关于 SQL 请求错误的回复，但我无法影响 Entity Framework 如何构建这些.

最佳答案

除了已接受的答案外，还应注意，如果您尝试将数据库中的更改保存在表上，则会抛出相同的异常(每个派生表必须有自己的别名)没有主键。

这是一个 known bug多年后仍未修复(出现在 MySQL 5.5.22 + .Net/Connector 6.5.4 on 04/04/12)。

我知道没有主键的表不是一个好主意，但由于 DDL 生成器中存在另一个错误，一些表的关联实体键的属性 StoreGeneratedPattern 设置为 None 是在没有主键的情况下创建的...

关于c# - MySql + Entity Framework = 每个派生表必须有自己的别名，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7056716/