Exec and sp_executesql in SQL Server

Reference: http://www.cnblogs.com/xbf321/archive/2008/11/02/1325067.html

Exec('Select * From tablename ')

 Declare   @ Slideavg   Real  Declare   @ Sql1   Nvarchar ( 1000  )  Set   @ Sql1  =  '  Select@ Slideavg= AVG (VAL) from S '  +  @ Stationid  +  '  Hn where channel_num =  '''  +  @ Channel_num  +  '''  And date_time> =  '''  +  Convert ( Nvarchar , @ Oldh , 120 ) +  '''  And date_time <=  '''  +  Convert ( Nvarchar , @ H24 , 120 ) +  '''' ExecSp_executesql@ Sql1, N'@ Slideavg Real Output',@ SlideavgOutput  If   @ Slideavg   Is   Not   Null   And   @ Slideavg  <>  ''  Begin  ......... End 

 

 

 Select  C0252_id, c0252_name, c0252_addr ,((  Select   Top   1 C0003_name From DBO. t0003_districtinfo Where C0003_code Like   '  %  '  +  Substring (C0003_areacode,1 , 4 ) +  '  %  ' ) +  '   '  + C0003_areaname) As  Areaname  From DBO. t0252_manufacturer