附一篇oracle实现 top x

在psql中使用 \h select 命令，可以得到以下帮助

jincheng=# \h select
命令：       SELECT
描述：       从资料表或视观表读取资料
语法：
[ WITH [ RECURSIVE ] with查询语句(with_query) [,...] ]
SELECT [ ALL | DISTINCT [ ON ( 表达式 [,...] ) ] ]
    * | 表达式 [ [ AS ] 输出名称 ] [,...]
    [ FROM from列表中项 [,...] ]
    [ WHERE 条件 ]
    [ GROUP BY 表达式 [,...] ]
    [ HAVING 条件 [,...] ]
    [ WINDOW 窗口名称 AS ( 窗口定义 ) [,...] ]
    [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] 查询 ]
    [ ORDER BY 表达式 [ ASC | DESC | USING 运算子 ] [ NULLS { FIRST | LAST } ] [,...] ]
    [ LIMIT { 查询所用返回记录的最大数量 | ALL } ]
    [ OFFSET 起始值 [ ROW | ROWS ] ]
    [ FETCH { FIRST | NEXT } [ 查询所用返回记录的最大数量 ] { ROW | ROWS } ONLY
]
    [ FOR { UPDATE | SHARE } [ OF 表名 [,...] ] [ NOWAIT ] [...] ]

from 列表中的项可以是下列内容之一

    [ ONLY ] 表名 [ * ] [ [ AS ] 化名 [ ( 列的化名 [,...] ) ] ]
    ( 查询 ) [ AS ] 化名 [ ( 列的化名 [,...] ) ]
-- More  --

SELECT * FROM TABLENAME LIMIT 5 OFFSET 1;

这条语句等价于MysqL中的

SELECT * FROM TABLENAME LIMIT 1,5;