休眠条件查询以获取特定列

一尘不染

休眠条件查询以获取特定列

mysql

我在代码中使用了条件查询。它总是会开火select * from ...

相反，我想忽略查询中的一列（字段），因为该字段以字节为单位存储大量数据。这会导致性能问题。

有人可以对此提出想法吗？

一些更新

我在查询中添加了一个投影，它创建了一个查询，例如…

select
    this_.TEMPLATE_ID as y0_,
    this_.TEMPLATE_NAME as y1_,
    this_.CREATE_DATE as y2_,
    this_.UPDATE_DATE as y3_,
    this_.STATUS_CODE as y4_,
    this_.USER_ID as y5_,
    this_.UPDATED_BY as y6_,
    this_.CATEGORY_ID as y7_,
    this_.PRACTICE_ID as y8_ 
from
    templates this_ 
inner join
    user user1_ 
        on this_.USER_ID=user1_.USER_ID 
inner join
    template_categories category2_ 
        on this_.CATEGORY_ID=category2_.CATEGORY_ID 
where
    y4_=? 
    and y8_=? 
    and y5_ in (
        ?, ?
    ) 
order by
    y1_ asc limit ?

现在的问题就像.. Unknown column 'y4_' in 'where clause'
和y8_的相同错误，y5_表示所有接近它给出错误的地方。

我将其修改为Query …

select
    this_.TEMPLATE_ID as y0_,
    this_.TEMPLATE_NAME as y1_,
    this_.CREATE_DATE as y2_,
    this_.UPDATE_DATE as y3_,
    this_.STATUS_CODE as y4_,
    this_.USER_ID as y5_,
    this_.UPDATED_BY as y6_,
    this_.CATEGORY_ID as y7_,
    this_.PRACTICE_ID as y8_ 
from
    templates this_ 
inner join
    user user1_ 
        on this_.USER_ID=user1_.USER_ID 
inner join
    template_categories category2_ 
        on this_.CATEGORY_ID=category2_.CATEGORY_ID 
where
    this_.STATUS_CODE=1
    and this_.PRACTICE_ID=1 
    and this_.USER_ID in (
        1, 2
    ) 
order by
    y1_ asc limit ?

而且有效。但是我不知道如何在HQL中对其进行修改？

阅读 263

2020-05-17

共1个答案

一尘不染

使用投影来指定您要返回的列。

例

SQL查询

SELECT user.id, user.name FROM user;

hibernate替代

Criteria cr = session.createCriteria(User.class)
    .setProjection(Projections.projectionList()
      .add(Projections.property("id"), "id")
      .add(Projections.property("Name"), "Name"))
    .setResultTransformer(Transformers.aliasToBean(User.class));

  List<User> list = cr.list();

2020-05-17