英文:
Sqlx "missing destination name" for struct tag through pointer
问题
我有一个像这样的模型：
type Course struct {
Name string `db:"course_name"`
}
type Group struct {
Course *Course
}
type Groups []Group
当我尝试使用以下查询对Groups进行sqlx.Select操作时：
SELECT c.name as course_name FROM courses as c;
我得到了一个错误信息：
> 在*main.Groups中缺少目标名称course_name
这段代码有什么问题？
英文:
I have a model like this:
type Course struct {
Name string `db:"course_name"`
}
type Group struct {
Course *Course
}
type Groups []Group
And when i try to do sqlx.Select for Groups with a query like this:
SELECT c.name as course_name FROM courses as c;
I get
> missing destination name course_name in *main.Groups
error.
What is the issue with this code?
答案1
得分: 3
在选择多行并将结果扫描到切片中时，您需要使用sqlx.Select，这适用于您的查询情况，如果只选择一行，请使用sqlx.Get。
此外，您不能直接将结果扫描到Group结构体中，因为它的字段没有标记（不像Course结构体），而且Course字段也没有嵌入。
请尝试以下代码：
course := Course{}
courses := []Course{}
db.Get(&course, "SELECT name AS course_name FROM courses LIMIT 1")
db.Select(&courses, "SELECT name AS course_name FROM courses")
英文:
You need to use sqlx.Select when you are selecting multiple rows and you want to scan the result into a slice, as is the case for your query, otherwise use sqlx.Get for a single row.
In addition, you can't scan directly into a Group struct because none of its fields are tagged (unlike the Course struct), and the Course field isn't embedded.
Try:
course := Course{}
courses := []Course{}
db.Get(&course, "SELECT name AS course_name FROM courses LIMIT 1")
db.Select(&courses, "SELECT name AS course_name FROM courses")
答案2
得分: 1
我将Course *Course更改为Course Course，但没有效果。
当我像这样嵌入它时：
type Group struct {
Course
}
它起作用了。
这也是有效的：
type Group struct {
*Course
}
看起来sqlx除了嵌入字段之外，不理解其他任何东西。
英文:
I changed Course *Course to Course Course - no effect.
When i made it embedded like this:
type Group struct {
Course
}
it worked.
This is also valid:
type Group struct {
*Course
}
Looks like sqlx doesn't understand anything except embedded fields.
答案3
得分: 1
好的，当你在使用带有Sqlx的嵌入式结构时，大小写是很重要的，至少在我的情况下是这样。
你需要在sql中引用嵌入的结构，像这样：
select name as "course.name" from courses...
注意，course是小写的，并且命名中包含表和列之间的点/句号。
然后你的Get或Select应该可以正常工作。
英文:
Ok, so when you are using an embbeded struct with Sqlx, capitalization is important, at least in my case.
You need to refer to the embedded struct in your sql, like so:
select name as "course.name" from courses...
Notice that course is lower case and the naming involves a dot/period between table and column.
Then your Get or Select should work just fine.
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