如何在存储过程内部获得查询的结果

declare @nn int  

declare @sql NVARCHAR(max)

declare @ParmDefinition as NVARCHAR(100)

SET @ParmDefinition = N'@RowNumber int output';

set @sql=N'SELECT  @RowNumber=count(*)  FROM PR_PostSet'

EXECUTE sp_executesql @sql,@ParmDefinition,@RowNumber=@nn output

print @nn