1. Data sources and datasets

• Data source — connection info (SQL Server, Azure SQL, Analysis Services, Oracle, ODBC, OLE DB, XML, SharePoint lists). Shared data sources live on the server and are reused; embedded ones live in one report.
• Credentials: Windows integrated (Kerberos needed for double-hop), stored credentials (required for subscriptions and caching), prompt user, none.
• Dataset — a query (text or stored procedure) + fields + parameters + filters. Shared datasets can be cached and reused across reports.

CREATE OR ALTER PROCEDURE rpt.usp_SalesByRegion @StartDate DATE, @EndDate DATE, @RegionIds VARCHAR(MAX)
AS
SELECT r.RegionName, p.Category, SUM(s.Amount) AS Amount, COUNT(*) AS Orders
FROM dbo.Sales s
JOIN dbo.Regions r ON r.RegionId = s.RegionId
JOIN dbo.Products p ON p.ProductId = s.ProductId
WHERE s.SaleDate >= @StartDate AND s.SaleDate < DATEADD(DAY, 1, @EndDate)
  AND s.RegionId IN (SELECT value FROM STRING_SPLIT(@RegionIds, ','))
GROUP BY r.RegionName, p.Category;

Best practice: keep heavy logic in SQL (stored procedures/views), return only the rows and columns the report shows.