如何在GO中连接到SQL数据库？

要连接Go中的SQL数据库，需使用database/sql包和特定数据库驱动。1. 导入database/sql包和驱动（如github.com/go-sql-driver/mysql），注意驱动前加下划线表示仅用于初始化；2. 使用sql.Open("mysql", "user:password@tcp(localhost:3306)/dbname")创建数据库句柄，并调用db.Ping()验证连接；3. 使用db.Query()执行查询，db.Exec()执行插入、更新或删除，并通过rows.Scan()读取结果，注意检查rows.Err()；4. 可配置连接池参数如db.SetMaxOpenConns(25)以优化性能。完整示例包含导入、连接、查询和资源释放，确保每步都处理错误，最终成功连接并操作数据库。

Connecting to a SQL database in Go is straightforward using the database/sql package, which provides a generic interface for SQL databases, along with a driver specific to the database you're using (like MySQL, PostgreSQL, SQLite, etc.).

Here’s how to do it step by step:

✅ 1. Import the Required Packages

You need two things:

• The database/sql package (standard Go library)
• A driver for your specific database

For example, if you're using PostgreSQL, you might use lib/pq or jackc/pgx; for MySQL, go-sql-driver/mysql; for SQLite, mattn/go-sqlite3.

Install the driver via go.mod (example for MySQL):

go get github.com/go-sql-driver/mysql

Then import in your code:

import (
    "database/sql"
    "fmt"
    _ "github.com/go-sql-driver/mysql" // Import driver (note the underscore)
)

? The _ means we import it for its side effects (initializing the driver), not to use it directly.

✅ 2. Open a Connection to the Database

Use sql.Open() to create a database handle. It doesn’t connect immediately but initializes the connection info.

db, err := sql.Open("mysql", "user:password@tcp(localhost:3306)/dbname")
if err != nil {
    panic(err)
}
defer db.Close() // Make sure to close when done

Replace the connection string depending on your DB:

• MySQL: "user:pass@tcp(localhost:3306)/mydb"
• PostgreSQL: "host=localhost user=usr password=pass dbname=mydb sslmode=disable" (with jackc/pgx)
• SQLite: "file:mydb.sqlite"

⚠️ sql.Open() may not return an error even if the DSN is wrong — it just prepares the connection. To test connectivity, use db.Ping().

err = db.Ping()
if err != nil {
    panic("could not connect to the database: "   err.Error())
}

✅ 3. Perform Queries

Once connected, you can run queries:

rows, err := db.Query("SELECT id, name FROM users")
if err != nil {
    panic(err)
}
defer rows.Close()

for rows.Next() {
    var id int
    var name string
    err := rows.Scan(&id, &name)
    if err != nil {
        panic(err)
    }
    fmt.Printf("ID: %d, Name: %s\n", id, name)
}

// Check for errors after iteration
if err = rows.Err(); err != nil {
    panic(err)
}

Use db.Exec() for INSERT, UPDATE, DELETE:

result, err := db.Exec("INSERT INTO users (name) VALUES (?)", "Alice")
if err != nil {
    panic(err)
}

lastID, err := result.LastInsertId()
if err != nil {
    panic(err)
}
fmt.Printf("Last inserted ID: %d\n", lastID)

✅ 4. Use Connection Pooling (Optional but Recommended)

Go’s sql.DB is designed to be long-lived and handles connection pooling automatically.

You can tune it:

db.SetMaxOpenConns(25)
db.SetMaxIdleConns(5)
db.SetConnMaxLifetime(5 * time.Minute)

This helps avoid resource exhaustion in production.

Full Working Example (MySQL)

package main

import (
    "database/sql"
    "fmt"
    "log"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    db, err := sql.Open("mysql", "root:password@tcp(127.0.0.1:3306)/testdb")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    err = db.Ping()
    if err != nil {
        log.Fatal("Failed to ping database:", err)
    }

    var version string
    err = db.QueryRow("SELECT VERSION()").Scan(&version)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("Database version:", version)
}

Summary

• Use database/sql a driver
• Call sql.Open() with correct DSN
• Always db.Ping() to verify connection
• Use Query, Exec, QueryRow for operations
• Let Go manage connections via pooling

It’s not complex, but easy to mess up DSN formatting or forget error checks after rows.Next().

Basically, that's all you need to get started connecting Go to a SQL database.

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