PolarDB:Connect to a database

First, you need to add the MySQL JDBC driver dependency in the pom.xml file. Code example:

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

Connect to the instance. Replace the parameters <HOST>, port number, <USER>, <PASSWORD>, <DATABASE>, <YOUR_TABLE_NAME>, and <YOUR_TABLE_COLUMN_NAME>.

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) {
      // PolarDB instance connection address, port, and database name to connect to
      String url = "jdbc:mysql://<HOST>:3306/<DATABASE>?useSSL=false&serverTimezone=UTC";
      // Database account
      String user = "<USER>";
      // 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();
         // Name of the data table to retrieve
         ResultSet rs = stmt.executeQuery("SELECT * FROM `<YOUR_TABLE_NAME>`");

         while(rs.next()) {
            // Name of the column in the data table to retrieve
            System.out.println(rs.getString("<YOUR_TABLE_COLUMN_NAME>"));
         }

         rs.close();
         stmt.close();
         conn.close();
      } catch (Exception var7) {
         var7.printStackTrace();
      }

   }
}

First, you need to install the PyMySQL library. If you have not installed it, you can install it using the following command:

pip3 install PyMySQL

Connect to the instance. Replace the parameters <HOST>, port number, <USER>, <PASSWORD>, <DATABASE>, and <YOUR_TABLE_NAME>.

import pymysql

# Database connection parameters
host = '<HOST>'  # PolarDB instance connection address
port = 3306  # Default port 3306
user = '<USER>'  # Database account
password = '<PASSWORD>'  # Password of the database account
database = '<DATABASE>'  # Database name to connect to

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

    # Obtain the operation cursor
    with connection.cursor() as cursor:
        # Execute SQL query
        sql = "SELECT * FROM `<YOUR_TABLE_NAME>`"  # Name of the data table to retrieve
        cursor.execute(sql)

        # Obtain 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()

First, you need to install the go-sql-driver/mysql driver. You can install it using the following command:

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

Connect to the instance. Replace the parameters <HOST>, port number, <USER>, <PASSWORD>, <DATABASE>, and <YOUR_TABLE_NAME>.

package main

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

func main() {
    // Database connection parameters
    dbHost := "<HOST>"       // PolarDB instance connection address
    dbPort := "3306"         // Default port 3306
    dbUser := "<USER>"       // Database account
    dbPass := "<PASSWORD>"   // Password of the database account
    dbName := "<DATABASE>"   // Database name to connect to

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

    // Open the 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)
    }

    // Create an operation cursor
    var result string
    err = db.QueryRow("SELECT VERSION()").Scan(&result)
    if err != nil {
        log.Fatalf("Failed to execute query: %v", err)
    }

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

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

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