Consulta datos con una marca de tiempo de confirmación

Consulta datos de una tabla que contiene una columna de confirmación TIMESTAMP.

Explora más

Para obtener documentación detallada en la que se incluye esta muestra de código, consulta lo siguiente:

• Confirma marcas de tiempo en bases de datos de dialecto de SQL estándar de Google
• Confirma marcas de tiempo en bases de datos de dialecto de PostgreSQL

Muestra de código

C#

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

using Google.Cloud.Spanner.Data;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

public class QueryDataWithTimestampColumnAsyncSample
{
    public class Album
    {
        public int SingerId { get; set; }
        public int AlbumId { get; set; }
        public DateTime? LastUpdateTime { get; set; }
        public long? MarketingBudget { get; set; }
    }

    public async Task<List<Album>> QueryDataWithTimestampColumnAsync(string projectId, string instanceId, string databaseId)
    {
        string connectionString = $"Data Source=projects/{projectId}/instances/{instanceId}/databases/{databaseId}";

        using var connection = new SpannerConnection(connectionString);
        using var cmd = connection.CreateSelectCommand("SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime FROM Albums ORDER BY LastUpdateTime DESC");

        var albums = new List<Album>();
        using var reader = await cmd.ExecuteReaderAsync();
        while (await reader.ReadAsync())
        {
            albums.Add(new Album
            {
                SingerId = reader.GetFieldValue<int>("SingerId"),
                AlbumId = reader.GetFieldValue<int>("AlbumId"),
                LastUpdateTime = reader.IsDBNull(reader.GetOrdinal("LastUpdateTime")) ? (DateTime?)null : reader.GetFieldValue<DateTime>("LastUpdateTime"),
                MarketingBudget = reader.IsDBNull(reader.GetOrdinal("MarketingBudget")) ? 0 : reader.GetFieldValue<long>("MarketingBudget")
            });
        }
        return albums;
    }
}

C++

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

void QueryDataWithTimestamp(google::cloud::spanner::Client client) {
  namespace spanner = ::google::cloud::spanner;

  spanner::SqlStatement select(
      "SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime"
      "  FROM Albums"
      " ORDER BY LastUpdateTime DESC");
  using RowType =
      std::tuple<std::int64_t, std::int64_t, absl::optional<std::int64_t>,
                 absl::optional<spanner::Timestamp>>;

  auto rows = client.ExecuteQuery(std::move(select));
  for (auto& row : spanner::StreamOf<RowType>(rows)) {
    if (!row) throw std::move(row).status();
    std::cout << std::get<0>(*row) << " " << std::get<1>(*row);
    auto marketing_budget = std::get<2>(*row);
    if (!marketing_budget) {
      std::cout << " NULL";
    } else {
      std::cout << ' ' << *marketing_budget;
    }
    auto last_update_time = std::get<3>(*row);
    if (!last_update_time) {
      std::cout << " NULL";
    } else {
      std::cout << ' ' << *last_update_time;
    }
    std::cout << "\n";
  }
}

Go

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

import (
	"context"
	"fmt"
	"io"
	"strconv"

	"cloud.google.com/go/spanner"
	"google.golang.org/api/iterator"
)

func queryWithTimestamp(w io.Writer, db string) error {
	ctx := context.Background()
	client, err := spanner.NewClient(ctx, db)
	if err != nil {
		return err
	}
	defer client.Close()

	stmt := spanner.Statement{
		SQL: `SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime
				FROM Albums ORDER BY LastUpdateTime DESC`}
	iter := client.Single().Query(ctx, stmt)
	defer iter.Stop()
	for {
		row, err := iter.Next()
		if err == iterator.Done {
			return nil
		}
		if err != nil {
			return err
		}
		var singerID, albumID int64
		var marketingBudget spanner.NullInt64
		var lastUpdateTime spanner.NullTime
		if err := row.ColumnByName("SingerId", &singerID); err != nil {
			return err
		}
		if err := row.ColumnByName("AlbumId", &albumID); err != nil {
			return err
		}
		if err := row.ColumnByName("MarketingBudget", &marketingBudget); err != nil {
			return err
		}
		budget := "NULL"
		if marketingBudget.Valid {
			budget = strconv.FormatInt(marketingBudget.Int64, 10)
		}
		if err := row.ColumnByName("LastUpdateTime", &lastUpdateTime); err != nil {
			return err
		}
		timestamp := "NULL"
		if lastUpdateTime.Valid {
			timestamp = lastUpdateTime.String()
		}
		fmt.Fprintf(w, "%d %d %s %s\n", singerID, albumID, budget, timestamp)
	}
}

Java

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

static void queryMarketingBudgetWithTimestamp(DatabaseClient dbClient) {
  // Rows without an explicit value for MarketingBudget will have a MarketingBudget equal to
  // null. A try-with-resource block is used to automatically release resources held by
  // ResultSet.
  try (ResultSet resultSet =
      dbClient
          .singleUse()
          .executeQuery(
              Statement.of(
                  "SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime FROM Albums"
                      + " ORDER BY LastUpdateTime DESC"))) {
    while (resultSet.next()) {
      System.out.printf(
          "%d %d %s %s\n",
          resultSet.getLong("SingerId"),
          resultSet.getLong("AlbumId"),
          // We check that the value is non null. ResultSet getters can only be used to retrieve
          // non null values.
          resultSet.isNull("MarketingBudget") ? "NULL" : resultSet.getLong("MarketingBudget"),
          resultSet.isNull("LastUpdateTime") ? "NULL" : resultSet.getTimestamp("LastUpdateTime"));
    }
  }
}

Node.js

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

// ...

// Imports the Google Cloud client library
const {Spanner} = require('@google-cloud/spanner');

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// const projectId = 'my-project-id';
// const instanceId = 'my-instance';
// const databaseId = 'my-database';

// Creates a client
const spanner = new Spanner({
  projectId: projectId,
});

// Gets a reference to a Cloud Spanner instance and database
const instance = spanner.instance(instanceId);
const database = instance.database(databaseId);

const query = {
  sql: `SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime
          FROM Albums ORDER BY LastUpdateTime DESC`,
};

// Queries rows from the Albums table
try {
  const [rows] = await database.run(query);

  rows.forEach(row => {
    const json = row.toJSON();

    console.log(
      `SingerId: ${json.SingerId}, AlbumId: ${
        json.AlbumId
      }, MarketingBudget: ${
        json.MarketingBudget ? json.MarketingBudget : null
      }, LastUpdateTime: ${json.LastUpdateTime}`
    );
  });
} catch (err) {
  console.error('ERROR:', err);
} finally {
  // Close the database when finished
  database.close();
}

PHP

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

use Google\Cloud\Spanner\SpannerClient;

/**
 * Queries sample data from a database with a commit timestamp column.
 *
 * This sample uses the `MarketingBudget` column. You can add the column
 * by running the `add_column` sample or by running this DDL statement against
 * your database:
 *
 *      ALTER TABLE Albums ADD COLUMN MarketingBudget INT64
 *
 * This sample also uses the 'LastUpdateTime' commit timestamp column. You can
 * add the column by running the `add_timestamp_column` sample or by running
 * this DDL statement against your database:
 *
 * 		ALTER TABLE Albums ADD COLUMN LastUpdateTime TIMESTAMP OPTIONS (allow_commit_timestamp=true)
 *
 * Example:
 * ```
 * query_data_with_timestamp_column($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function query_data_with_timestamp_column(string $instanceId, string $databaseId): void
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $results = $database->execute(
        'SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime ' .
        ' FROM Albums ORDER BY LastUpdateTime DESC'
    );

    foreach ($results as $row) {
        if ($row['MarketingBudget'] == null) {
            $row['MarketingBudget'] = 'NULL';
        }
        if ($row['LastUpdateTime'] == null) {
            $row['LastUpdateTime'] = 'NULL';
        }
        printf('SingerId: %s, AlbumId: %s, MarketingBudget: %s, LastUpdateTime: %s' . PHP_EOL,
            $row['SingerId'], $row['AlbumId'], $row['MarketingBudget'], $row['LastUpdateTime']);
    }
}

Python

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

def query_data_with_timestamp(instance_id, database_id):
    """Queries sample data from the database using SQL.

    This updates the `LastUpdateTime` column which must be created before
    running this sample. You can add the column by running the
    `add_timestamp_column` sample or by running this DDL statement
    against your database:

        ALTER TABLE Performances ADD COLUMN LastUpdateTime TIMESTAMP
        OPTIONS (allow_commit_timestamp=true)

    """
    spanner_client = spanner.Client()
    instance = spanner_client.instance(instance_id)

    database = instance.database(database_id)

    with database.snapshot() as snapshot:
        results = snapshot.execute_sql(
            "SELECT SingerId, AlbumId, MarketingBudget FROM Albums "
            "ORDER BY LastUpdateTime DESC"
        )

    for row in results:
        print("SingerId: {}, AlbumId: {}, MarketingBudget: {}".format(*row))

Ruby

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Ver en GitHubComentarios

# project_id  = "Your Google Cloud project ID"
# instance_id = "Your Spanner instance ID"
# database_id = "Your Spanner database ID"

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new project: project_id
client  = spanner.client instance_id, database_id

client.execute("SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime
                FROM Albums ORDER BY LastUpdateTime DESC").rows.each do |row|
  puts "#{row[:SingerId]} #{row[:AlbumId]} #{row[:MarketingBudget]} #{row[:LastUpdateTime]}"
end

¿Qué sigue?

Para buscar y filtrar muestras de código en otros productos de Google Cloud, consulta el navegador de muestra de Google Cloud.