英文:
How do you select the whole table in postgres using golang sql?
问题
我对posgres和Go都比较新手,但是我已经在这个问题上苦苦挣扎了一段时间。我目前正在尝试发送一个查询以从表中检索所有内容。
当我在postgres中尝试使用
SELECT * FROM land_registry_price_paid_uk
时,它会显示所有内容,但是当我使用Query进行相同操作时,我得到了以下错误信息。
sql: 期望在Scan中有16个目标参数,而不是1个
这是我目前的代码。
fmt.Printf("user: %s, password: %s, dbName: %s", user, password, dbName)
connectionString := fmt.Sprintf("user=%s password=%s dbname=%s sslmode=%s", user, password, dbName, "disable")
var err error
a.DB, err = sql.Open("postgres", connectionString)
if err != nil {
log.Fatal(err)
}
rows, err := a.DB.Query("SELECT ( * ) FROM land_registry_price_paid_uk")
if err != nil {
log.Fatal(err)
}
defer rows.Close()
println(rows)
for rows.Next() {
var name string
if err := rows.Scan(&name); err != nil {
log.Fatal(err)
}
fmt.Printf("this is something: %s\n", name)
非常感谢您的帮助。
英文:
I'm fairly new to posgres and Go, but have been struggling for a while on this. I'm currently trying to send a query to retrieve everything from a table.
When I try to use
SELECT * FROM land_registry_price_paid_uk
within postgres, it shows everything, but when I do the same using Query, I get.
sql: expected 16 destination arguments in Scan, not 1
This is the current code that I have.
fmt.Printf("user: %s, password: %s, dbName: %s", user, password, dbName)
connectionString := fmt.Sprintf("user=%s password=%s dbname=%s sslmode=%s", user, password, dbName, "disable")
var err error
a.DB, err = sql.Open("postgres", connectionString)
if err != nil {
log.Fatal(err)
}
rows, err := a.DB.Query("SELECT ( * ) FROM land_registry_price_paid_uk")
if err != nil {
log.Fatal(err)
}
defer rows.Close()
println(rows)
for rows.Next() {
var name string
if err := rows.Scan(&name); err != nil {
log.Fatal(err)
}
fmt.Printf("this is something: %s\n", name)
Any help is appreciated.
答案1
得分: 3
看起来你的查询工作正常,你返回了16列的数据,并尝试将它们全部扫描到一个字符串变量中,你需要为每一列提供一个变量:
var name string
// 其他列的变量放在这里
// 然后按照表的顺序将变量作为参数引用到row.Scan中
if err := rows.Scan(&name); err != nil {
log.Fatal(err)
}
如果你之前没有使用过sql/go,你可能还需要了解处理可空值的特殊类型,因为你可能也会需要它们:
更新:
为了进一步说明,假设你有一个包含以下字段的三列表:
- id (int)
- name (string)
- optional_data (string, 可空)
你可以按照以下方式读取行(未经测试):
var (
id int
name string
optionalData sql.NullString
)
if err := rows.Scan(&id, &name, &optionalData); err != nil {
log.Fatal(err)
}
英文:
Looks like your query is working just fine, you are returning 16 columns of data and trying to scan them all into a single string variable, you will need to provide a holder variable for each column:
var name string
// vars to hold other column values go here
// then reference vars in table order as args to row.Scan below
if err := rows.Scan(&name); err != nil {
log.Fatal(err)
}
if you have not used sql/go before you may also want to look into the special types provided for coping with nullable values as you will likely need these as well:
Update:
To further illustrate, say you had a three column table which consisted of the following fields:
- id (int)
- name (string)
- optional_data (string, nullable)
You might read the row as follows (not tested):
var (
id int
name string
optionalData sql.NullString
)
if err := rows.Scan(&id, &name, &optionalData); err != nil {
log.Fatal(err)
}
答案2
得分: 1
非常感谢,这对我很有帮助。但是我想再添加一点信息。
嗯,我不知道你使用的是哪个版本的goalng,但我在Windows/386上使用的是1.11.2版本。当我添加了括号后,它就无法正常工作了,但是如果没有括号,它就可以完美运行。
请使用以下代码:
rows, err := a.DB.Query("SELECT * FROM mytable")
而不是:
rows, err := a.DB.Query("SELECT ( * ) FROM mytable")
这是我的示例代码:
rows, err := db.Query("SELECT * FROM words")
if err != nil {
log.Fatal(err)
}
defer rows.Close()
println(rows)
for rows.Next() {
var word, exa1, exa2, mean string
var id int
if err := rows.Scan(&id, &word, &exa1, &exa2, &mean); err != nil {
log.Fatal(err)
}
fmt.Printf("id: %d\n word: %s \n example1: %s \n example2: %s \n meaning: %s\n---\n\n", id, word, exa1, exa2, mean)
}
希望这对你有用。
英文:
Thanks a lot it was useful for me. but I would like to add a little bit more of information.
well I don't know what is your goalng's version but I'm using version 1.11.2 on windows/386 but when I added the parentheses this not worked. but without them it run perfect.
use this:
rows, err := a.DB.Query("SELECT * FROM mytable")
instead of :
rows, err := a.DB.Query("SELECT ( * ) FROM mytable")
and here is my example:
rows, err := db.Query("SELECT * FROM words")
if err != nil {
log.Fatal(err)
}
defer rows.Close()
println(rows)
for rows.Next() {
var word, exa1, exa2, mean string
var id int
if err := rows.Scan(&id, &word, &exa1, &exa2, &mean); err != nil {
log.Fatal(err)
}
fmt.Printf("id: %d\n word: %s \n example1: %s \n example2: %s \n meaning: %s\n---\n\n", id, word, exa1, exa2, mean)
}
I hope this will be useful.
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