SQL Server语法，用于通过子查询进行更新

How do I formulate this query

我如何制定此查询

update forge..dimInteg2
   set duplicates = 
      (select count(*) from (select idCover 
                                 from x90..dimCover
                                 group by idCover
                                 having count(*) > 1)) 
where dimTable = 'dimCover'
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