英文:
How to append URI as string in SQL query
问题
看起来很简单，但我无法实现它。
当浏览domain.com/post/1时，应该显示id值为1的行的数据。
行id是整数（int4）。
以下是代码，但它不起作用：
package mainimport "fmt"import "github.com/go-martini/martini"import "net/http"import "database/sql"import _ "github.com/lib/pq"func SetupDB() *sql.DB {db, err := sql.Open("postgres", "user=postgres password=apassword dbname=lesson4 sslmode=disable")PanicIf(err)return db}func PanicIf(err error) {if err != nil {panic(err)}}func main() {m := martini.Classic()m.Map(SetupDB())m.Get("/post/:idnumber", func(rw http.ResponseWriter, r *http.Request, db *sql.DB) {rows, err := db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)PanicIf(err)defer rows.Close()var title, author, description stringfor rows.Next() {err:= rows.Scan(&title, &author, &description)PanicIf(err)fmt.Fprintf(rw, "Title: %s\nAuthor: %s\nDescription: %s\n\n",title, author, description)}})m.Run()}
英文:
Looks simple but I unable to make it happen.
When browsing domain.com/post/1, it should show data from row id which value 1.
Row id is integer (int4).
Below the the codes, which is not working:
package mainimport "fmt"import "github.com/go-martini/martini"import "net/http"import "database/sql"import _ "github.com/lib/pq"func SetupDB() *sql.DB {db, err := sql.Open("postgres", "user=postgres password=apassword dbname=lesson4 sslmode=disable")PanicIf(err)return db}func PanicIf(err error) {if err != nil {panic(err)}}func main() {m := martini.Classic()m.Map(SetupDB())m.Get("/post/:idnumber", func(rw http.ResponseWriter, r *http.Request, db *sql.DB) {rows, err := db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)PanicIf(err)defer rows.Close()var title, author, description stringfor rows.Next() {err:= rows.Scan(&title, &author, &description)PanicIf(err)fmt.Fprintf(rw, "Title: %s\nAuthor: %s\nDescription: %s\n\n",title, author, description)}})m.Run()}
答案1
得分: 1
你的问题的一部分是你在 SQL 查询中使用了字符串 params["idnumber"]。
db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)
这将查找一个 id 等于 params["idnumber"] 字符串的书籍。
你需要使用占位符和参数，参考 http://golang.org/pkg/database/sql/#DB.Query
在这种情况下，你的查询应该是：
db.Query("SELECT title, author, description FROM books WHERE id=$1", params["idnumber"])
这应该解决你遇到的问题。然而，在你实际更新你的问题并提供实际问题之前，我无法确定。
更新
你得到的错误 undefined: params 是因为你的作用域中没有 params 对象。
我建议你阅读一下 martini 如何在路由中获取参数的工作原理。https://github.com/go-martini/martini#routing
英文:
Part of your issue is that you're using the string params["idnumber"] as part of the SQL query
db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)
That will look for a book where the id equals params["idnumber"] string.
What you need to do is use placeholders and the arguments according to http://golang.org/pkg/database/sql/#DB.Query
In this case your query should be
db.Query("SELECT title, author, description FROM books WHERE id=$1", params["idnumber"])
That should solve the issue I think you're having. However, until you actually update your question with the actual issue you're having I won't know.
Update
The error you're getting with undefined: params is because you don't have a params object in scope.
I'd suggest reading how martini works in regards of getting the arguments out of the route. https://github.com/go-martini/martini#routing
答案2
得分: 1
我认为问题在于你在字符串文字查询中使用了变量名，而你想要的是它的值。
尝试将这段代码进行更改：
rows, err := db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)
改为：
rows, err := db.Query("SELECT title, author, description FROM books WHERE id =$1", params["idnumber"])
除此之外，你可能还有其他问题，但是考虑到你没有正确构建查询，我不会期望你能得到你想要的结果。
英文:
I think the problem is that you're using the variable name in your string literal query, you want it's value there instead.
Try changing this;
rows, err := db.Query(`SELECT title, author, description FROM books WHERE id = params["idnumber"]`)
to;
rows, err := db.Query("SELECT title, author, description FROM books WHERE id =$1", params["idnumber"])
You could have other issues beyond that but given you're not forming the query correctly I wouldn't expect you to get back the results you want.
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