How to use database in Go?

With the widespread popularity of web applications and other complex applications on the Internet, databases have become an indispensable part. Go is a popular programming language that can be used for web application and other system development. In this article, we will explore how to use databases in Go.

1. Select a database

Before you start using a database, you first need to choose a database that is suitable for your application. Go supports many popular databases such as MySQL, PostgreSQL, MongoDB, etc. You can also use an ORM (Object Relational Mapper) library or a SQL generator library to simplify database interaction. An ORM library is a library that maps objects to tables in a database, while a SQL generator library is a library for creating and querying SQL queries. Choosing a database should be based on your application needs and your understanding of the advantages and disadvantages of different databases.

2. Install the database driver

Once you have selected your database, the next step is to install the database driver. Go has drivers for various databases, you can use drivers from Go's standard library database/sql or external libraries with higher-level functionality. It is crucial to obtain the correct information for the driver from the official documentation of the database. Depending on the database you choose, the requirements will differ, so please be aware of some details to pay attention to during the installation process.

3. Establishing a connection

Before using the database, you need to establish a connection to the database. In Go, you can use the following code to create a connection to a MySQL database:

package main

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

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/mydb")
    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    err = db.Ping()
    if err != nil {
        panic(err.Error())
    }

    fmt.Println("Connection established")
}

In this example, we use the sql.Open() function to open a MySQL database connection. In the Open() function, we use the MySQL driver (in this case github.com/go-sql-driver/mysql) to tell Go that we want to connect Database name, username, password and address. Then, we use the db.Ping() command to test whether the connection to the database is successful to ensure that the connection is successful. Finally, use defer db.Close() to ensure the database connection is closed before the program exits.

4. Execute queries

Once the connection to the database is established, you can start using it. To execute a query statement, you can use the db.Query() or db.QueryRow() function. The db.Query() function is used to execute queries that return multiple rows, while the db.QueryRow() function is used to execute queries that return a single row of results.

The following is an example for executing a query:

package main

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

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/mydb")
    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    rows, err := db.Query("SELECT * FROM mytable")
    if err != nil {
        panic(err.Error())
    }
    defer rows.Close()

    for rows.Next() {
        var id int
        var name string
        err = rows.Scan(&id, &name)
        if err != nil {
            panic(err.Error())
        }
        fmt.Println("id:", id, "name:", name)
    }

    err = rows.Err()
    if err != nil {
        panic(err.Error())
    }
}

In the above example code, we first use db.Query() to execute the SELECT statement and store the results in the rows variable. Then, we use the rows.Close() function to close the result set. Next, we use rows.Next() to loop through each row in the result set and use the rows.Scan() function to match the results with variables. Finally, we use the rows.Err() function to handle any potential errors.

5. Perform insert, update and delete operations

In addition to query operations, the database also supports insert, update and delete operations. Performing these operations in Go is similar to query operations, you need to use different functions.

To perform an insert operation, you can use the following code:

res, err := db.Exec("INSERT INTO mytable (name) VALUES (?)", "John")
if err != nil {
    panic(err.Error())
}
lastInsertID, err := res.LastInsertId()
if err != nil {
    panic(err.Error())
}
fmt.Println("Last inserted ID:", lastInsertID)

To perform an update operation, you can use the following code:

res, err = db.Exec("UPDATE mytable SET name = ? WHERE id = ?", "John Doe", 1)
if err != nil {
    panic(err.Error())
}
rowsAffected, err := res.RowsAffected()
if err != nil {
    panic(err.Error())
}
fmt.Println("Rows affected:", rowsAffected)

To perform a delete operation, you can use The following code:

res, err = db.Exec("DELETE FROM mytable WHERE id = ?", 1)
if err != nil {
    panic(err.Error())
}
rowsAffected, err = res.RowsAffected()
if err != nil {
    panic(err.Error())
}
fmt.Println("Rows affected:", rowsAffected)

6. Using transactions

Using database transactions is very important to ensure the integrity of the database when making any changes. In Go, you can use transactions using the following code:

tx, err := db.Begin()

stmt, err := tx.Prepare("INSERT INTO mytable (name) VALUES (?)")
if err != nil {
    tx.Rollback()
    panic(err.Error())
}

_, err = stmt.Exec("John")
if err != nil {
    tx.Rollback()
    panic(err.Error())
}

stmt, err = tx.Prepare("UPDATE mytable SET name = ? WHERE id = ?")
if err != nil {
    tx.Rollback()
    panic(err.Error())
}

_, err = stmt.Exec("John Doe", 1)
if err != nil {
    tx.Rollback()
    panic(err.Error())
}

err = tx.Commit()
if err != nil {
    panic(err.Error())
}

In the above code, we first start a transaction using the db.Begin() function. Then, we use the tx.Prepare() function to prepare the SQL statement to be executed. Next, we use the stmt.Exec() function to execute the SQL statement. After all operations are performed, we commit the transaction using the tx.Commit() function. If any operation fails, we use the tx.Rollback() function to roll back all changes.

7. Reference

In this article, we introduced how to use databases in Go. For more advanced database operations, you can use an ORM or SQL generator library for easier interaction. To learn more details about using a specific database, please consult the relevant official documentation and Go library documentation. Here are some references:

• Database/SQL for Golang: https://golang.org/pkg/database/sql/
• Go MySQL Driver: https:// github.com/go-sql-driver/mysql
• Go PostgreSQL driver: https://github.com/lib/pq
• MongoDB Go driver: https://github .com/mongodb/mongo-go-driver

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