A strange SQL statement

 

 Create   Table Test77 (djbh Varchar ( 10 ), SPDM Varchar ( 10 ), SL Int  )  Insert   Into Test77 Values ( '  Ja001  ' ,'  A  ' , 4  )  Insert   Into Test77 Values ( '  Ja001  ' , '  B  ' , 3  ) Insert   Into Test77 Values ( '  Ja002  ' , '  A  ' , 5  )  Insert   Into Test77 Values ( '  Ja003 ' , '  A  ' , 2  )  Insert   Into Test77 Values ( '  Ja004  ' , '  A  ' , 2 )  Insert   Into Test77 Values ( '  Ja005  ' , '  A  ' , 2  )  Insert   Into Test77 Values ( ' Ja006  ' , '  A  ' , 2 )

 

Select max (djbh) from test77 A where 17> = (select sum (SL) from test77 B where. djbh> B. djbh and. SPDM = B. SPDM) and SPDM = 'A' this syntax is very strange, do not understand ..