golang gets query results

In order to obtain query results, Golang provides different methods and tools. In this article, we'll explore methods and techniques for obtaining query results.

1. Using a database driver

Using a database driver is a common method of obtaining query results. Golang supports a variety of database drivers, including MySQL, PostgreSQL, and SQLite. Before using the database driver, you need to install the corresponding library. For example, in order to use the MySQL driver, you need to run the following command:

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

This will download and install the MySQL driver.

Next, you need to use the database/sql package to execute the query and get the results. Below is a sample program that uses the MySQL driver to connect to a MySQL database and execute a simple SELECT query:

package main

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

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

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

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

In the above program, we use the sql.Open() method to connect to MySQL database. In the connection string, we specify the database server’s hostname, port, and database name. Then, we use the db.Query() method to execute the SELECT query and the row data in the query's result set. For each row, we use the rows.Scan() method to read the column data in the row.

2. Using the ORM framework

The ORM (Object Relational Mapping) framework is another popular method of obtaining query results in Golang. The ORM framework allows you to map database tables into structures and fields in Golang and provides various methods to perform queries and manipulate the database. Some of the popular ORM frameworks in Golang include GORM, XORM, Beego ORM, etc.

The following is a sample program that uses the GORM framework to obtain query results:

package main

import (
    "fmt"
    "gorm.io/driver/mysql"
    "gorm.io/gorm"
)

type User struct {
    ID   uint
    Name string
}

func main() {
    dsn := "user:password@tcp(hostname:port)/database"
    db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    var users []User
    db.Find(&users)

    for _, user := range users {
        fmt.Println(user.ID, user.Name)
    }
}

In the above program, we use GORM to map the User table to the User structure in Golang. We then execute the SELECT query using the db.Find() method and save the query results into a slice. Finally, we iterate over the slice to print each user's ID and name.

3. Using HTTP client

If you need to get query results from a web service, you can use Golang's built-in HTTP client. HTTP clients allow you to send requests to web services with HTTP interfaces and get results from the responses.

The following is a sample program that uses an HTTP client to obtain query results:

package main

import (
    "encoding/json"
    "fmt"
    "net/http"
)

type User struct {
    ID   int    `json:"id"`
    Name string `json:"name"`
}

func main() {
    url := "https://example.com/users"
    resp, err := http.Get(url)
    if err != nil {
        panic(err.Error())
    }
    defer resp.Body.Close()

    var users []User
    err = json.NewDecoder(resp.Body).Decode(&users)
    if err != nil {
        panic(err.Error())
    }

    for _, user := range users {
        fmt.Println(user.ID, user.Name)
    }
}

In the above program, we use the http.Get() method to request a user list from a Web service. We then decode the JSON formatted response using the json.NewDecoder() method and map it into the User slice. Finally, we iterate over the slice to print each user's ID and name.

Summary

The above are three common ways to obtain query results in Golang: using a database driver, using an ORM framework and using an HTTP client. These tips can help you write efficient and flexible code to better process and obtain query results. Whether you're getting query results from a relational database or from a Web service, these tips can help you easily get the results and process them.

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