Using MySQL in Go: avoid five common mistakes

The Go language is increasingly becoming a popular programming language, just like the database MySQL. This article will introduce five common mistakes when using MySQL in Go language so that developers can avoid these mistakes and improve the quality and stability of the code.

Error 1: Not closing the database connection

When using MySQL, it is best to manually close the database connection after use. If the connection is not closed promptly, system resources will be wasted and database performance may decrease. To avoid this happening, developers need to make sure the connection is closed when writing code. Here is a sample code snippet that demonstrates how to properly close a database connection:

// 创建数据库连接
db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/database")

// 检查错误
if err != nil {
    log.Fatal(err)
}

// 明确关闭数据库连接
defer db.Close()

Note the defer statement in the code. This statement will be executed when the function returns, ensuring that the database connection is closed after use.

Error 2: Unhandled error

When using MySQL, errors may occur at any time, including: database connection failure, query statement error, incorrect parameters, etc. Developers need to ensure that these errors are handled accurately to prevent the program from terminating abnormally. Here is a sample code snippet that demonstrates how to check for errors and handle them:

// 执行SQL查询
rows, err := db.Query("SELECT name FROM users WHERE id = ?", 1)

// 检查错误
if err != nil {
    log.Fatal(err)
}

// 关闭 rows 对象，注意 defer
defer rows.Close()

// 遍历结果
for rows.Next() {
    var name string
    err := rows.Scan(&name)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(name)
}

Note the if statement and log.Fatal() in the code. This statement will interrupt program execution when an error occurs and output an error message.

Error 3: Unable to handle NULL values ​​correctly

In MySQL, NULL is a special value that represents a missing or unknown value. When using MySQL, developers need to determine whether a table field is NULL and handle NULL values ​​correctly. Here is a sample code snippet that demonstrates how to properly handle NULL values:

// 执行SQL查询
rows, err := db.Query("SELECT name, age FROM users WHERE id = ?", 1)

// 检查错误
if err != nil {
    log.Fatal(err)
}

// 关闭 rows 对象，注意 defer
defer rows.Close()

// 遍历结果
for rows.Next() {
    var name string
    var age sql.NullInt64
    err := rows.Scan(&name, &age)
    if err != nil {
        log.Fatal(err)
    }
    // 处理 NULL 值
    if age.Valid {
        fmt.Println(name, age.Int64)
    } else {
        fmt.Println(name, "Age is NULL")
    }
}

Note the sql.NullInt64 type and the if statement in the code. This code will determine whether the age field is NULL when processing NULL values. If so, print "Age is NULL", otherwise print the age value.

Error 4: Using SQL statements to splice strings

Using strings to splice SQL statements is a common mistake. This approach is vulnerable to SQL injection attacks and is not conducive to code maintenance. To avoid this happening, developers can use SQL placeholders and parameters. Here is a sample code snippet that demonstrates how to use placeholders and parameters:

// 定义 SQL 查询和占位符
query := "SELECT name FROM users WHERE age > ? AND gender = ?"

// 准备参数
args := []interface{}{18, "M"}

// 执行 SQL 查询
rows, err := db.Query(query, args...)
if err != nil {
    log.Fatal(err)
}

// 关闭 rows 对象，注意 defer
defer rows.Close()

// 遍历结果
for rows.Next() {
    var name string
    err := rows.Scan(&name)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(name)
}

Note the placeholders and parameter args in the code. This code uses placeholders when querying, replacing possible SQL injection attacks with parameters.

Error 5: Not using connection pool technology

Connection pool technology is a commonly used database optimization technology, which can reduce the load pressure on the database server and improve system performance. When using MySQL, developers need to use connection pooling technology to manage database connections. The following is a sample code snippet that demonstrates how to use connection pooling technology:

// 创建连接池
db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/database")
if err != nil {
    log.Fatal(err)
}
db.SetMaxIdleConns(10)
db.SetMaxOpenConns(100)

// 执行 SQL 查询
rows, err := db.Query("SELECT name FROM users WHERE age > ?", 18)
if err != nil {
    log.Fatal(err)
}

// 关闭 rows 对象，注意 defer
defer rows.Close()

// 遍历结果
for rows.Next() {
    var name string
    err := rows.Scan(&name)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(name)
}

Note SetMaxIdleConns() and SetMaxOpenConns() in the code. This code will use connection pooling technology to manage database connections and limit the maximum number of connections.

Summary

When using MySQL in the Go language, developers need to avoid some common mistakes. These errors include not closing the database connection, not handling errors, failing to handle NULL values ​​correctly, using SQL statements to concatenate strings, and not using connection pooling technology. By avoiding these errors, developers can improve the quality and stability of their code while improving system performance.

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