有没有一种可移植的方式来“选择第一个10 *来自T”语义？ [英] Is there a portable way to have "SELECT FIRST 10 * FROM T" semantic?

问题描述

我想从数据库中读取10k记录块中的数据。

I want to read data in blocks of say 10k records from a database.

我发现结果限制，很明显这不能用sql以便携方式完成。

I found Result limits on wikipedia and it seems obvious that this can't done with sql in a portable way.

另一种方法可能是 JdbcTemplate 提供了许多查询方法，但我怎么能确定已经读取了足够的行。通过RowMapper和ResultSetExtractor等回调，无法指示已读取足够的数据。

Another approach could be JdbcTemplate which offers many methods for queries, but how could I decide that enough rows have been read. Through the callbacks like RowMapper and ResultSetExtractor it can't be indicated, that enough data has been read.

编辑：我在寻找JdbcTemplate的解决方案
这个帖子建议使用 setMaxRows 我忽略了。

I was looking for a solution for JdbcTemplate This post suggests to use setMaxRows which I had overlooked.

推荐答案

抓取 Hibernate 或 JPA 。两者都熟悉各种数据库方言，并且会透明地处理令人讨厌的数据库细节。

Grab Hibernate or JPA. Both are familiar with various database dialects and will handle the nasty DB specifics under the hoods transparently.

在Hibernate中你可以使用 条件#setFirstResult（） 和 标准＃setMaxResults（） 。例如

In Hibernate you can paginate using Criteria#setFirstResult() and Criteria#setMaxResults(). E.g.

List users = session.createCriteria(User.class)
    .addOrder(Order.asc("id"))
    .setFirstResult(0) // Index of first row to be retrieved.
    .setMaxResults(10) // Amount of rows to be retrieved.
    .list();

在JPA中你可以使用 查询#setFirstResult（） 和 Query＃setMaxResults （） 。

In JPA you can do similar using Query#setFirstResult() and Query#setMaxResults().

List users = em.createQuery("SELECT u FROM User u ORDER BY u.id");
    .setFirstResult(0) // Index of first row to be retrieved.
    .setMaxResults(10) // Amount of rows to be retrieved.
    .getResultList();

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