英文:
Go Using db.Query to return more than one column
问题
在Go SQL文档中，他们给出了一个示例在这里，该查询只返回一个列（在我看来是个糟糕的示例，至少应该返回两个...）
age := 27
rows, err := db.Query("SELECT name FROM users WHERE age=?", age)
if err != nil {
log.Fatal(err)
}
for rows.Next() {
var name string
if err := rows.Scan(&name); err != nil {
log.Fatal(err)
}
fmt.Printf("%s is %d\n", name, age)
}
if err := rows.Err(); err != nil {
log.Fatal(err)
}
文档在这里说明了
Scan将当前行的列复制到dest指向的值中。
如果我有一个结构体，比如说我有一个结构体
type User struct{
Name string
Age int
}
并且我将查询修改为SELECT name, age from users where age=?
如何将*Rows解包到我的结构体中？我找到了这个示例，但它没有涉及到结构体。我将遵循Active Record模式的约定，因此我的结构体将通过蛇形转换映射到我的数据库。
英文:
In the Go SQL docs they give an example here of a query that only returns 1 column (poor example in my opinion, at least return 2...)
age := 27
rows, err := db.Query("SELECT name FROM users WHERE age=?", age)
if err != nil {
log.Fatal(err)
}
for rows.Next() {
var name string
if err := rows.Scan(&name); err != nil {
log.Fatal(err)
}
fmt.Printf("%s is %d\n", name, age)
}
if err := rows.Err(); err != nil {
log.Fatal(err)
}
The docs state here that
Scan copies the columns in the current row into the values pointed at by dest.
How does this work with a struct, lets say I have a struct
type User struct{
Name string
Age int
}
and I modify my query to SELECT name, age from users where age=?
How do I unpack *Rows into my struct? I did find this example, but it didn't deal with structs. I will be following Active Record pattern conventions so my structs will map to my database via snake case conversion.
答案1
得分: 4
根据源代码，似乎使用...语法在目标指针上进行复制：
func (rs *Rows) Scan(dest ...interface{}) error
所以在你的例子中，你可以这样做：
for rows.Next() {
u := User{} // 一个空的用户
...
if err := rows.Scan(&u.Name, &u.Age); err != nil {
...
}
}
只要传递了确切数量的指针，无论它们是来自结构体还是其他地方，这应该都可以工作。
英文:
Looking at the source, it seems the copy is done with ... syntax on destination pointers:
func (rs *Rows) Scan(dest ...interface{}) error
So in your example, you can do for instance:
for rows.Next() {
u := User{} // An empty user
...
if err := rows.Scan(&u.Name, &u.Age); err != nil {
...
}
}
As long as you pass the exact number of pointers, this should work, whether they are from a struct or not.
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