Scott Andersen

Highlight all the columns in the group header and right click / "Group Columns". This will create a grouped header section.  You can then put the "Group Header" text element on the grouped section, and remove the cells for the individual columns.

A few clarifications:
- where is the date picker you are looking at?
- The default selected date is usually the current date, or the default date set in the parameter properties in Studio.
- Are you wanting to make the first day of the week be set to Sunday rather than Monday?

This is a known issue targeted for future release.

Your approach is fairly sound, although you might try checking the report in as an organization based user, which will change the path (removing the organization specific portion of the path.) With the org infor present it may make it so that the report doesn't work for a non-root user.
From a general strategy pint of view, here is some details on how to use multiple data sources in a report:
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A report in JRS is actually a Report Unit, and a ReportUnit is not designed to use multiple data sources (JasperReports data sources). So if your data does not come from the same database (with which you may still pass the REPORT_CONNECTION to your subdataset) or is using the same JSON (for which you could derive a sub dataset), your best option is using data adapters. Any DatasetRun in JasperReports can run against a data adapter specified as a property.
You can create a ReportUnit referencing a (JRS) datasource, i.e. FoodMart. This is not mandatory.
Then, we assume that the chart gets its data from some JSON and the subreport uses an SQL query from a different database.
A Data Adapter in JRS is an xml resource that is uploaded either manually, or by using JSS.
The “binding” between a DatasetRun (which is the part of the report that defines how a subdataset gets its data), and the data adapter is configured in Jaspersoft Studio.
For a subreport, the main dataset will set the property net.sf.jasperreports.data.adapter
For Charts, Tables etc, it is always about using this property (Studio provides also the UI to specify the data adapter)
Be sure you point to a proper data adapter, which is a resource, inside your repository, just like you would do when you reference an image.
Studio will help you also loading these data adapters when the report is published to JRS.
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You need to upgrade in stages - see the latest Upgrade guide: 
https://community.jaspersoft.com/documentation/tibco-jasperreports-server-upgrade-guide/v790/upgrading-jasperreports-server-64x-or
 

The first step is to track down the phrase "Caused by" in the log. This will further isolate the problem.
There appears to be a permissions problem, based on "The SELECT permission was denied on the object 'Clientes', database 'WEB', schema 'dbo'". Try confirming that the user being use to connect has the correct access.

Try puttting the subreport on the Summary band, and make the Summary band page height equal to the Report page height.  This shoudl force the Summary to be printed on a new page.

Jaspersoft Studio can produce reports that utilize data from both a database and a CSV file. This data must be in separate queries and consumed in separate sub-reports / charts / tables, because CSV data is not queryable and as such cannot be joined together with data from a RDBMS data source. You could drive the report from the CSV file and do separate queries to get the additional data from the RDBMS, but this would not perform well for large volumes of data since a separate DB call would execute for each row of data from the CSV file.
Jaspersoft is also not designed to load CSV files upon execution of a report. You can accomplish what you are doing by using Jaspersoft’s REST API services. These services can be called from your application directly or via Jaspersoft’s ETL tool.  The ETL tool can also be used to load the CSV data into an RDBMS so that the information can be joined together.
Here’s a link to the REST API doco:
http://community.jaspersoft.com/documentation/tibco-jasperreports-server-rest-api-reference/v630/rest-api-overview