Hibernate HQL NULL比较模式 [英] Hibernate HQL NULL comparison pattern

问题描述

想象一个简单的网页，您可以像这样搜索预订：

网页图片http://locuslive.com/webdrive/booking.png

• 如果预订号字段不已填充，我要返回所有行。


• 如果预订号字段以返回该行。

我在Hibernate中使用了一个模式（使用底层的MySQL数据库） ：

  AND（：bookingNum IS NULL或（：bookingNum IS NOT NULL AND：bookingNum = booking.bookingNumber））
  

我最近看到一些奇怪的性能问题，让我想知道是否有更好的模式在这里使用。我肯定非Hibernate查询必须有类似的问题。

其他人在这种情况下做什么？

谢谢，

D。

解决方案

使用Hibernate条件查询，仅当bookingNum不为null时才添加谓词。 / p>

Imagine a simple web page allowing you to search Bookings like this:

picture of web page http://locuslive.com/webdrive/booking.png

• If the Booking Number field is not populated I want to return all rows.
• If the Booking Number field is populated I only want to return that row.

I have been using a pattern in Hibernate (with an underlying MySQL database) to accomplish this that goes something like:

AND (:bookingNum IS NULL OR (:bookingNum IS NOT NULL AND :bookingNum = booking.bookingNumber))

I've recently been seeing some weird performance issues and that got me wondering if there is a better pattern to use here. I'm sure non-Hibernate queries must have similar issues.

What do others do in this siutation?

Thanks,

D.

解决方案

Use a Hibernate criteria query, adding the predicate only if bookingNum isn't null.

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