Question

我在GO中有一个查询，它从mysql返回一个不同的响应。

这是查询：

SELECT DISTINCT 
        questions.id as question_id, 
        questions.question, 
        questions.priority, 
        questions.type
    FROM questions 
    LEFT JOIN profile ON profile.user_id = ? 
    LEFT JOIN group ON group.user_id = profile.user_id  
    WHERE questions.status = 1 
    AND group.status = 1 
    AND questions.id NOT IN (SELECT DISTINCT question_id FROM answers WHERE user_id = profiles.user_id)

当我在mysql终端上运行它时，它没有按预期返回任何内容。但是当我尝试在GO语言上运行它时，它有一个不应该被返回的返回，因为它已经在NOT IN子句中被过滤，这是所有已回答的问题。当我尝试将profiles.user_id更改为特定值时，它返回预期的输出。

我认为使用列参数不能在GO中工作。如果我将users.profile更改为特定变量，但是有其他查询需要使用该功能才能实现我的预期输出，这将是一个快速解决方案。

我尝试使用stmt.Prepared语句和db.Query（）具有相同的结果

转到代码：

query :=    "    SELECT DISTINCT " +
        "        questions.id as question_id, " +
        "        questions.question, " +
        "        questions.priority, " +
        "        questions.type " +
        "    FROM questions " +
        "    LEFT JOIN profile ON profile.user_id = 1627 " +
        "    LEFT JOIN group ON group.user_id = profile.user_id  " +
        "    WHERE questions.status = 1 " +
        "    AND group.status = 1 " +
        "    AND questions.id NOT IN (SELECT DISTINCT question_id FROM answers WHERE user_id = profiles.user_id); "

stmt, err := db.Prepare(query)
if err != nil {
    checkErr(err) // proper error handling instead of panic in your app
}
defer stmt.Close() // Close the statement when we leave main() / the program terminates

userId := json.userId

args := []interface{}{}
args = append(args, userId)

start := time.Now()
rows, err := stmt.Query(args...)
elapsed := time.Since(start)

if err != nil {
    checkErr(err) // proper error handling instead of panic in your app
}

// Fetch rows
for rows.Next() {
    // get RawBytes from data
    err = rows.Scan(&question.QuestionId, &question.Question, &question.Priority, &question.Type)
    questions = append(questions, question)
    if err != nil {
        checkErr(err) // proper error handling instead of panic in your app
    }
}
defer rows.Close()
defer db.Close()

有没有可行的解决方法？

感谢您的回复

Answer 1

您可以使用问号＆＃39;？＆＃39;在您期望参数的地方的查询中：

age := 27
rows, err := db.Query("SELECT name FROM users WHERE age=?", age)
if err != nil {
        log.Fatal(err)
}
defer rows.Close()
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)
}

此外，你可以在代码中使用back tick来表示多行字符串（而不是用+连接）。这将使您的代码更容易阅读。

query :=    `SELECT DISTINCT
    questions.id as question_id, 
    questions.question, 
    questions.priority, 
    questions.type 
FROM questions 
LEFT JOIN profile ON profile.user_id = 1627 
LEFT JOIN group ON group.user_id = profile.user_id  
WHERE questions.status = 1 
AND group.status = 1 
AND questions.id NOT IN (SELECT DISTINCT question_id FROM answers WHERE user_id = profiles.user_id); `

Go语言查询列引用不起作用

1 个答案: