Subreport not working on sql express

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SQL

ı have sqlexpress and visual studio 13
ı buıld a report with subreport.
it is not working as ;Data retrieval failed for the subreport, , located at:c:\x.
but the subreport works alone.

in the log file
ServiceStartThread: Exception caught while starting service. Error: Microsoft.ReportingServices.Library.ReportServerDatabaseUnavailableException: The report server cannot open a connection to the report server database. A connection to the database is required for all requests and processing. ; System.Data.SqlClient.SqlException:

is there a limitation in sql express for subreports

What I have tried:

ı buıld a report with subreport.
it is not working as ;Data retrieval failed for the subreport, , located at:c:\x.
but the subreport works alone.