Query Row Count for All Tables
You can simply use this :

SELECT sc.name +'.'+ ta.name TableName
 ,SUM(pa.rows) RowCnt
 FROM sys.tables ta
 INNER JOIN sys.partitions pa
 ON pa.OBJECT_ID = ta.OBJECT_ID
 INNER JOIN sys.schemas sc
 ON ta.schema_id = sc.schema_id
 WHERE ta.is_ms_shipped = 0 AND pa.index_id IN (1,0)
 GROUP BY sc.name,ta.name
 ORDER BY SUM(pa.rows) DESC


Various other methods include:here


sys.partitions Catalog View
sys.dm_db_partition_stats Dynamic Management View (DMV)
sp_MSforeachtable System Stored Procedure
COALESCE() Function