Joined reports are groupings of report “blocks” that create useful multiple views of your data. Each joined report can contain up to five report blocks. Each block contains customizable data, including summaries, and custom formulas, with data sorted by the filters of your choice. Joined reports are particularly useful for summarizing large amounts of data, held across objects, very quickly.
Joined reports are particularly useful for summarizing large amounts of data, held across objects, very quickly.
https://help.salesforce.com/s/articleView?id=sf.reports_joined_create.htm&type=5
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