Django MySQL不同查询获取多个值 [英] Django MySQL distinct query for getting multiple values

问题描述

我有一个 MySQL 数据库不幸与 Django 1.4.1一起使用。
如果我正确的话，区分功能只适用于POSTGRESQL。

我必须使一个不同的查询由多个值组成，而只有不同的一个，

这一个适用于POSTGRE，但不适用于MYSQL，
我收到以下错误;

DISTINCT ON字段是不支持此数据库后端

  staff = Staff.objects.order_by（'person__full_name'） .distinct（'person__full_name'）
  

然后我尝试了

$ $ $ $ $ $ $ $ $ $$$$$$$$$ >

但是我没有得到不同的价值观，因为我也得到了工作人员的工作类别。但是当我不包含它，我不能得到它作为数组。

任何想法？

解决方案

.distinct（[* fields]）只适用于PostgresSQL 。

From distinct 文档

这里有区别。对于正常的distinct（）调用，数据库会在确定哪些行不同时比较每行中的每个字段。对于具有指定字段名称的distinct（）调用，数据库将仅比较指定的字段名称。

如所述，记录中的所有字段都被检查。很可能在你的情况下，你得到不同字段值的记录（更可能的情况是，如果你查询多个表ManyToMany或ForeignKey关系）。

为了合并为数组可以参考以前的问题 Django查询不同价值观工作，但我无法使用查询结果

I have a MySQL database unfortunately used with Django 1.4.1. Distinct function is only working for POSTGRESQL if i get it right.

I have to make a distinct query consist of multiple values while only distinct one,

Like; This one works for POSTGRE but not with MYSQL, I get the following error;

DISTINCT ON fields is not supported by this database backend

staff = Staff.objects.order_by('person__full_name').distinct('person__full_name')

Then I tried

staff = Staff.objects.values('person__full_name','staff_job_categories').distinct().order_by('person__full_name')

But I do not get distinct values because i get also the staff job categories. But when I dont contain it I could not get it as array.

Any idea ?

解决方案

.distinct([*fields]) only works in PostgresSQL.

From distinct documentation

Here's the difference. For a normal distinct() call, the database compares each field in each row when determining which rows are distinct. For a distinct() call with specified field names, the database will only compare the specified field names.

As stated all fields in a record are checked. Mostly likely in your case you are getting records with different field values (more likely a case if you are queries multiple tables ManyToMany or ForeignKey relations).

For consolidating as array you can refer your earlier question Django Query distinct values works but i cant use the query result

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