Hvis du vil oprette et indeks og gøre forespørgslen hurtigere, tilføj [Index]-attributten til attributten og generer automatisk koden som følger:
Vi opdaterer databasen, og fejlen er som følger:
System.Data.SqlClient.SqlException (0x80131904): table 'dbo. Kolonnen 'Telefon' i 'Konto' kan ikke bruges som nøglekolonne i et indeks.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action'1 wrapCloseInAction)
at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action'1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
I System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
In System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource'1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, boolesk inRetry)
I System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
I System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher. <NonQuery>b__0(DbCommand t, DbCommandInterceptionContext'1 c)
I System.Data.Entity.Infrastructure.Interception.InternalDispatcher'1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func'3 operation, TInterceptionContext interceptionKontekst, Handling'3 udfører, Handling'3 udført)
I System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.NonQuery(DbCommand kommando, DbCommandInterceptionContext interceptionContext)
I System.Data.Entity.Internal.InterceptableDbCommand.ExecuteNonQuery()
I System.Data.Entity.Migrations.DbMigrator.ExecuteSql(MigrationStatement migrationStatement, DbConnection connection, DbTransaction transaction, DbInterceptionContext aflytningKontekst)
I System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ExecuteSql(MigrationStatement migrationStatement, DbConnection connection, DbTransaction-transaktion , DbInterceptionKontekst aflytningKontekst)
I System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable'1 migrationStatements, DbConnection-forbindelse, DbTransaction-transaktion, DbInterceptionKontekst aflytningKontekst)
I System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsWithinTransaction(IEnumerable'1 migrationStatements, DbTransaction-transaktion, DbInterceptionContext aflytningKontekst)
I System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsWithinNewTransaction(IEnumerable'1 migrationStatements, DbConnection-forbindelse, DbInterceptionContext aflytningKontekst)
I System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable'1 migrationStatements, DbConnection-forbindelse, DbInterceptionContext interceptionContext)
på System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable'1 migrationStatements, DbConnection connection)
på System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClass32. <ExecuteStatements>b__30()
I System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1. <Execute>b__0()
at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func'1 operation)
I System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation)
I System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable'1 migrationStatements, DbTransaction existingTransaction)
I System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable'1 migrationStatements)
på System.Data.Entity.Migrations.Infrastructure.MigratorBase.ExecuteStatements(IEnumerable'1 migrationStatements)
I System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, VersionedModel targetModel, IEnumerable'1 operations, IEnumerable'1 systemOperations, Boolean nedgradering, boolesk auto)
på System.Data.Entity.Migrations.DbMigrator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
på System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
på System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable'1 pendingMigrations, streng targetMigrationId, streng lastMigrationId)
på System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable'1 pendingMigrations, Streng targetMigrationId, Streng lastMigrationId)
på System.Data.Entity.Migrations.DbMigrator.UpdateInternal(Streng targetMigration)
I System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClasse. <Update>b__d()
på System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
på System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
på System.Data.Entity.Migrations.DbMigrator.Update(Streng targetMigration)
I System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(Streng targetMigration)
på System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.RunCore()
I System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run()
ClientConnectionId:2b5f614b-caab-4be6-bc1b-a813b7356739
Fejlnummer: 1919, Stat: 1, Klasse: 16
Bord-dbo. Kolonnen 'Telefon' i 'Konto' kan ikke bruges som nøglekolonne i et indeks.
Årsagen til fejlen er, at alle strengegenskaber for ef som standard er af typen NVARCHAR(Max),
Løsningen er som følger:
Udfør længden af strengen
Som vist på billedet, er skabelsen en succes!
|
Opslået på 23/11/2017 18.47.15
|
|
|
|
