Mostrar cantidad de registros de todas las tablas de una BD

 SELECT

      QUOTENAME(SCHEMA_NAME(sOBJ.schema_id)) + '.' + QUOTENAME(sOBJ.name) AS [TableName]
      , SUM(sPTN.Rows) AS [RowCount]
FROM 
      sys.objects AS sOBJ
      INNER JOIN sys.partitions AS sPTN
            ON sOBJ.object_id = sPTN.object_id
WHERE
      sOBJ.type = 'U'
      AND sOBJ.is_ms_shipped = 0x0
      AND index_id < 2 -- 0:Heap, 1:Clustered
GROUP BY 
      sOBJ.schema_id
      , sOBJ.name
ORDER BY [TableName]
GO

Fuente: https://www.mssqltips.com/sqlservertip/2537/sql-server-row-count-for-all-tables-in-a-database/