3.6、提取该查询的第x行

postgres=# FETCH ABSOLUTE 2 from tbase_cur ;                
 id | nickname  
----+-----------
  2 | TBase好
(1 row)
postgres=# FETCH ABSOLUTE -1 from tbase_cur ; 
 id |  nickname  
----+------------
  5 | TBase swap
(1 row)
postgres=# FETCH ABSOLUTE -2 from tbase_cur ; 
 id |   nickname    
----+---------------
  4 | TBase default
(1 row)

X为负数时则从尾部向上提