MySQL插入Float32和Float64 Go

Question

I'm trying to insert a row into a MySQL table:

package main

import (
    "strconv"
    "io/ioutil"
    "strings"
    "os/exec"
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    temp_cpu := getCPUTemp() // returns float32
    temp_gpu := getGPUTemp() // returns float64

    db, err := sql.Open("mysql", "user:pass@/sysStats")
    handleError(err)

    _, err = db.Query("INSERT INTO temperatures (id, cpu, gpu, timestamp) VALUES (?, ?, ?, ?)", 1, temp_gpu, temp_cpu, time.Now())
    handleError(err)

    db.Close()
    return
}

It builds successfully but when I run the resulting binary it just times out after a long time with a generic timeout error.

The table has the following schema:

+----------------+-----------+------+-----+---------+-------+
| Field          | Type      | Null | Key | Default | Extra |
+----------------+-----------+------+-----+---------+-------+
| idtemperatures | int(11)   | NO   | PRI | NULL    |       |
| cpu            | float     | YES  |     | NULL    |       |
| gpu            | float     | YES  |     | NULL    |       |
| timestamp      | timestamp | YES  |     | NULL    |       |
+----------------+-----------+------+-----+---------+-------+

I am running this on the same server the MySQL instance is hosted and I can access the database with the user/password from the terminal.

Any help?

Thanks!

Answer 1

The id / primary key field in your db is called "idtemperatures" and you used "id" in your SQL statement.

Also since you're not executing a query (but an INSERT), you should use the DB.Exec() method to execute it. You should never use DB.Query() to execute DML (Data Manipulation Language) statements.

You may get a timeout error if you can't connect to your database. Make sure it uses default protocol (TCP) and host (localhost:3306). Another reason may be because you used DB.Query() to execute your SQL INSERT statement, and DB.Query() returns an *sql.Rows value which holds a database connection until you close it with the Rows.Close() method - which you never do; you didn't even store the returned db.Rows value.

Also you should call db.Close() as a deferred statement, right after the error check after opening it.

Corrected example:

db, err := sql.Open("mysql", "user:pass@/sysStats")
if err != nil {
    fmt.Println("Failed to open DB:", err)
    return
}
defer db.Close()

s := "INSERT INTO temperatures (idtemperatures, cpu, gpu, timestamp) VALUES (?, ?, ?, ?)"
res, err = db.Exec(s, 1, temp_gpu, temp_cpu, time.Now())

if err != nil {
    fmt.Println("Failed to execute INSERT:", err)
} else {
    n, err := res.RowsAffected()
    fmt.Println("INSERT executed, rows affected: ", n, err)
}