Grails findAll有排序，顺序，最大和偏移量？ [英] Grails findAll with sort, order, max and offset?

问题描述

我想在findAll查询中整合排序，顺序，最大值和偏移量。以下工作正常：

  def books = Book.findAll（from Book as b where b.approved = true order by b .dateCreated desc，[max：max，offset：offset]）
  

但是我想要的是：
$ b

  def books = Book.findAll（from Book as b where b.approved = true，[sort：'dateCreated' ，order：'desc'，max：max，offset：offset]）
  

这是行不通的。如何重写这个？

解决方案

HQL不支持排序和顺序作为参数，所以您需要包含order by作为HQL表达式的一部分

  def books = Book.findAll（from Book as b where b.approved = true
 +order by b.dateCreated desc，[max：max，offset：offset]）
  

（或者在这种情况下，只需使用 Book.findAllByApproved（true，[...]）而不是HQL）。 b

所以如果排序和顺序是变量，你需要一个技巧，比如

  def books = Book。 
 +（params.sort？order by b。$ {params.sort} $ {params.order}：''），$ b $（Book from b where b.approved = b [max：max，offset：offset]）
  

I want to integrate sort, order, max and offset in a findAll query. The following works fine:

def books = Book.findAll("from Book as b where b.approved=true order by b.dateCreated  desc", [max: max, offset: offset])

But what I want is:

def books = Book.findAll("from Book as b where b.approved=true", [sort: 'dateCreated', order: 'desc', max: max, offset: offset])

This does not work. How do I have to rewrite this?

解决方案

HQL doesn't support sort and order as parameters, so you need to include the "order by" as part of the HQL expression

def books = Book.findAll("from Book as b where b.approved=true"
  + " order by b.dateCreated desc", [max: max, offset: offset])

(or in this case just use Book.findAllByApproved(true, [...]) instead of HQL).

So if the sort and order are variables you need a trick like

def books = Book.findAll("from Book as b where b.approved=true"
  + (params.sort ? " order by b.${params.sort} ${params.order}" : ''), 
  [max: max, offset: offset])

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