Connect to a database

Add the MySQL JDBC driver dependency to the pom.xml file.

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.27</version>
</dependency>

Connect to the instance. Replace <HOST>, the port number, <USER>, <PASSWORD>, <DATABASE>, <YOUR_TABLE_NAME>, and <YOUR_TABLE_COLUMN_NAME> with your actual information.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class DatabaseConnection {
   public DatabaseConnection() {
   }

   public static void main(String[] args) {
      // The endpoint, port, and name of the PolarDB-X instance.
      String url = "jdbc:mysql://<HOST>:3306/<DATABASE>?useSSL=false&serverTimezone=UTC";
      // The database account.
      String user = "<USER>";
      // The password of the database account.
      String password = "<PASSWORD>";

      try {
         Class.forName("com.mysql.cj.jdbc.Driver");
         Connection conn = DriverManager.getConnection(url, user, password);
         Statement stmt = conn.createStatement();
         // The data table to be queried.
         ResultSet rs = stmt.executeQuery("SELECT * FROM `<YOUR_TABLE_NAME>`");

         while(rs.next()) {
            // The column to be retrieved.
            System.out.println(rs.getString("<YOUR_TABLE_COLUMN_NAME>"));
         }

         rs.close();
         stmt.close();
         conn.close();
      } catch (Exception e) {
         e.printStackTrace();
      }

   }
}

Install the PyMySQL library.

pip3 install PyMySQL

Connect to the instance. Replace <HOST>, the port number, <USER>, <PASSWORD>, <DATABASE>, and <YOUR_TABLE_NAME> with your actual information.

import pymysql

# Database connection parameters
host = '<HOST>'  # The endpoint of the PolarDB-X instance.
port = 3306  # The default port is 3306.
user = '<USER>'  # The database account.
password = '<PASSWORD>'  # The password of the database account.
database = '<DATABASE>'  # The name of the database to which you want to connect.

try:
    # Create a database connection.
    connection = pymysql.connect(
        host=host,
        port=port,
        user=user,
        passwd=password,
        db=database
    )

    # Get a cursor.
    with connection.cursor() as cursor:
        # Execute an SQL query.
        sql = "SELECT * FROM `<YOUR_TABLE_NAME>`"  # The data table to be queried.
        cursor.execute(sql)

        # Fetch the query results.
        results = cursor.fetchall()
        for row in results:
            print(row)

finally:
    # Close the database connection.
    if 'connection' in locals() and connection.open:
        connection.close()

Install the go-sql-driver/mysql driver.

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

Connect to the instance. Replace <HOST>, the port number, <USER>, <PASSWORD>, <DATABASE>, and <YOUR_TABLE_NAME> with your actual information.

package main

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

func main() {
    // Database connection parameters
    dbHost := "<HOST>"       // The endpoint of the PolarDB-X instance.
    dbPort := "3306"         // The default port is 3306.
    dbUser := "<USER>"       // The database account.
    dbPass := "<PASSWORD>"   // The password of the database account.
    dbName := "<DATABASE>"   // The name of the database to which you want to connect.

    // Build the Data Source Name (DSN).
    dsn := fmt.Sprintf("%s:%s@tcp(%s:%s)/%s?charset=utf8mb4&parseTime=True&loc=Local", dbUser, dbPass, dbHost, dbPort, dbName)

    // Open a database connection.
    db, err := sql.Open("mysql", dsn)
    if err != nil {
        log.Fatalf("Failed to connect to database: %v", err)
    }
    defer db.Close()

    // Test the connection.
    err = db.Ping()
    if err != nil {
        log.Fatalf("Failed to ping database: %v", err)
    }

    // Query the database version.
    var result string
    err = db.QueryRow("SELECT VERSION()").Scan(&result)
    if err != nil {
        log.Fatalf("Failed to execute query: %v", err)
    }

    // Print the database version.
    fmt.Printf("Connected to database, version: %s\n", result)

    // Execute an SQL query.
    rows, err := db.Query("SELECT * FROM `<YOUR_TABLE_NAME>`") // The data table to be queried.
    if err != nil {
        log.Fatalf("Failed to execute query: %v", err)
    }
    defer rows.Close()

    // Process the query results.
    for rows.Next() {
        var id int
        var name string
        if err := rows.Scan(&id, &name); err != nil {
            log.Fatalf("Failed to scan row: %v", err)
        }
        fmt.Printf("ID: %d, Name: %s\n", id, name)
    }

    // Check for iteration errors.
    if err := rows.Err(); err != nil {
        log.Fatalf("Error during iteration: %v", err)
    }
}