英文:
Why go-sql-driver fails to handle NULL in MySQL bigint field?
问题
我正在使用go-sql-driver连接到MySQL数据库。在我的一个表中，我使用了一个名为queue_length的BIGINT字段。默认情况下，该字段为NULL。当我尝试使用Golang中的go-sql-driver查询表中的所有字段时，结果集中包括queue_length在内的字段都没有显示出来。
在我的用例中，
表字段
[unique_id, qid, title, text, queue_length, user_id, date_created, last_updated]
当我执行以下代码时，我可以获取到queue_length之前的字段的值，但是结果集中没有[queue_length, user_id, date_created, last_updated]这些字段。
但是，如果我不选择queue_length，所有字段都会显示在结果集中。我在代码中将queue_length扫描到类型为int64的queueLength变量中。来自表的值为NULL。我尝试过类型转换，但没有成功。
这是go-sql-driver的一个bug还是我做错了什么？有人可以帮助我吗？
func GetQueues(uniqueId string) ([]*objects.Queue, error) {
db, err := GetDBConnection()
defer db.Close()
rows, err := db.Query("SELECT qid, title, text, queue_length, user_id, date_created, last_updated FROM queue WHERE unique_id = ?", uniqueId)
if err != nil {
panic(err.Error())
}
defer rows.Close()
var qId string
var title string
var text string
var userId string
var dateCreated string
var lastUpdated string
var queueLength int64
var queue *objects.Queue
var queues []*objects.Queue
for rows.Next() {
err = rows.Scan(&qId, &title, &text, &queueLength, &userId, &dateCreated, &lastUpdated)
queue = &objects.Queue{ QId: qId, Title: title, Text: text, UniqueId: uniqueId, UserId: userId, DateCreated: dateCreated, LastUpdated: lastUpdated, QueueLength: queueLength }
queues = append(queues, queue)
}
err = rows.Err()
if err != nil {
panic(err.Error())
return nil, err
}
return queues, err
}
英文:
I am using go-sql-driver to connect to MySQL database. In one of my table I am using a field called queue_length as BIGINT. This field is NULL by default. When I try to query all the fields from the table using go-sql-driver in Golang, the fields after queue_length are not coming in the result set including queue_length.
In my use case,
Table fields
[unique_id, qid, title, text, queue_length, user_id, date_created, last_updated]
When I execute the following code I am getting values for fields before queue_length but [queue_length, user_id, date_created, last_updated] fields are not coming in result set.
But if I don't select queue_length, all fields are coming in result set. I am scanning queue_length in queueLength variable in code which is of type int64. The value coming from table is NULL. I tried type conversion also. Didn't work.
Is this a bug in go-sql-driver or am I doing anything wrong? Could anyone help me with this?
func GetQueues(uniqueId string) ([]*objects.Queue, error) {
db, err := GetDBConnection()
defer db.Close()
rows, err := db.Query("SELECT qid, title, text, queue_length, user_id, date_created, last_updated FROM queue WHERE unique_id = ?", uniqueId)
if err != nil {
panic(err.Error())
}
defer rows.Close()
var qId string
var title string
var text string
var userId string
var dateCreated string
var lastUpdated string
var queueLength int64
var queue *objects.Queue
var queues []*objects.Queue
for rows.Next() {
err = rows.Scan(&qId, &title, &text, &queueLength, &userId, &dateCreated, &lastUpdated)
queue = &objects.Queue{ QId: qId, Title: title, Text: text, UniqueId: uniqueId, UserId: userId, DateCreated: dateCreated, LastUpdated: lastUpdated, QueueLength: queueLength }
queues = append(queues, queue)
}
err = rows.Err()
if err != nil {
panic(err.Error())
return nil, err
}
return queues, err
}
答案1
得分: 4
queueLength 应该是一个 NullInt64，而不是一个 int64。
var queueLength sql.NullInt64
在 Go 中，int 不能为 nil，所以 Scan 无法将 NULL 保存在 queueLength 中。
英文:
queueLength should be a NullInt64 instead of an int64.
var queueLength sql.NullInt64
In Go ints can't be nil so there's no way for Scan to save NULL in queueLength.
答案2
得分: 0
我使用这个工具来处理空值和零值字段，它包含了许多数据类型。
GitHub的链接是https://github.com/guregu/null。
英文:
I use this tool for Null and Zero fields, it includes many data types.
The github url is https://github.com/guregu/null
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