How to use Go language to query and sort data in MySQL database

With the continuous development of digital technology, a large amount of data used in our lives continues to accumulate. In order to utilize this data more efficiently, we need to use databases for data storage, query and processing in system development. Among them, MySQL, as a commonly used relational database management system, is widely used in various application scenarios.

As the amount of data increases, how to sort the MySQL database has become a very important issue. This article will introduce how to use Go language to query and sort data in MySQL database, so that you can process massive data more conveniently.

1. Go language to connect to MySQL database

Before we perform MySQL database query sorting, we first need to use Go language to connect to the MySQL database. Here we use Go's database/sql package for database connection and operations. The specific steps are as follows:

1. Introduce the necessary packages

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

Introduced the Go database/sql package and the MySQL driver package github.com/go-sql into the code -driver/mysql, these two packages are very important in connecting to the MySQL database.

2. Connect to MySQL database

func ConnectDB() (db *sql.DB, err error) {
    dsn := "user:password@tcp(127.0.0.1:3306)/database_name?charset=utf8mb4"
    db, err = sql.Open("mysql", dsn)
    if err != nil {
        return nil, err
    }
    err = db.Ping()
    if err != nil {
        return nil, err
    }
    return db, nil
}

In the function ConnectDB, we use the sql.Open() method to create a handle to the SQL database and call the Ping method. Determine whether the connection is successfully established.

3. Close the connection

func CloseDB(db *sql.DB) {
    err := db.Close()
    if err != nil {
        log.Printf("close db error:%v
", err)
    }
}

After completing the data operation, we should close the database connection in time and release resources.

2. Data query sorting

1. Query all data

After using Go language to connect to the MySQL database, we can start the data query operation . The following is a sample code for querying all data:

func QueryAllUsers(db *sql.DB) ([]*User, error) {
    users := make([]*User, 0)
    rows, err := db.Query("SELECT * FROM users ORDER BY age DESC")
    if err != nil {
        return nil, err
    }
    defer rows.Close()
    for rows.Next() {
        user := new(User)
        err := rows.Scan(&user.Id, &user.Name, &user.Age, &user.Address)
        if err != nil {
            return nil, err
        }
        users = append(users, user)
    }
    if err := rows.Err(); err != nil {
        return nil, err
    }
    return users, nil
}

Among them, we use the db.Query() method to query data from the MySQL database and sort it in descending order of the age field. Then use the rows.Next() method to read the query results row by row into the struct type data model, and append the data to the users slice. Finally, return users.

2. Specify query conditions

In actual situations, we often need to obtain specific data based on the required query conditions. The following is a sample code for specifying query conditions:

func QueryUsersByAge(db *sql.DB, age int) ([]*User, error) {
    users := make([]*User, 0)
    rows, err := db.Query("SELECT * FROM users WHERE age > ? ORDER BY age DESC", age)
    if err != nil {
        return nil, err
    }
    defer rows.Close()
    for rows.Next() {
        user := new(User)
        err := rows.Scan(&user.Id, &user.Name, &user.Age, &user.Address)
        if err != nil {
            return nil, err
        }
        users = append(users, user)
    }
    if err := rows.Err(); err != nil {
        return nil, err
    }
    return users, nil
}

In this example, we use the db.Query() method to query all data in the database whose age is greater than age, and sort them in descending order of the age field.

3. Conclusion

MySQL database is widely used in corporate and personal applications. For common needs such as data query and sorting, we can easily implement it using Go language. This article provides sample code for connecting to the MySQL database and performing data query and sorting, hoping to help readers better master the related technologies of the Go language and the application of the MySQL database.

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