在标准的可选部分有这样做的方法，但是很多数据库都支持自己的方法.

There are ways of doing this in optional parts of the standard, but a lot of databases support their own way of doing it.

一个非常好的讨论这个和其他事情的网站是 http://troels.arvin.dk/db/rdbms/#select-limit.

A really good site that talks about this and other things is http://troels.arvin.dk/db/rdbms/#select-limit.

PostgreSQL 和 MySQL 基本上都支持非标准的:

Basically, PostgreSQL and MySQL supports the non-standard:

SELECT...
LIMIT y OFFSET x 

Oracle、DB2 和 MSSQL 支持标准窗口函数:

Oracle, DB2 and MSSQL supports the standard windowing functions:

SELECT * FROM (
  SELECT
    ROW_NUMBER() OVER (ORDER BY key ASC) AS rownumber,
    columns
  FROM tablename
) AS foo
WHERE rownumber <= n

(我只是从上面链接的站点复制的，因为我从不使用这些数据库)

(which I just copied from the site linked above since I never use those DBs)

更新:从 PostgreSQL 8.4 开始支持标准的窗口函数，所以希望第二个示例也适用于 PostgreSQL.

Update: As of PostgreSQL 8.4 the standard windowing functions are supported, so expect the second example to work for PostgreSQL as well.

更新: SQLite 在 2018 年 9 月 15 日的 3.25.0 版本中添加了窗口函数支持，因此这两种形式也可以在 SQLite 中使用.

Update: SQLite added window functions support in version 3.25.0 on 2018-09-15 so both forms also work in SQLite.