使用参数查询数据

使用参数查询数据。

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如需查看包含此代码示例的详细文档，请参阅以下内容：

代码示例

C++

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

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

  spanner::SqlStatement select(
      "SELECT SingerId, FirstName, LastName FROM Singers"
      " WHERE LastName = @last_name",
      {{"last_name", spanner::Value("Garcia")}});
  using RowType = std::tuple<std::int64_t, std::string, std::string>;
  auto rows = client.ExecuteQuery(std::move(select));
  for (auto& row : spanner::StreamOf<RowType>(rows)) {
    if (!row) throw std::move(row).status();
    std::cout << "SingerId: " << std::get<0>(*row) << "\t";
    std::cout << "FirstName: " << std::get<1>(*row) << "\t";
    std::cout << "LastName: " << std::get<2>(*row) << "\n";
  }

  std::cout << "Query completed for [spanner_query_with_parameter]\n";
}

C#

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 


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

public class QueryWithParameterAsyncSample
{
    public class Singer
    {
        public int SingerId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

    public async Task<List<Singer>> QueryWithParameterAsync(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, FirstName, LastName FROM Singers WHERE LastName = @lastName",
            new SpannerParameterCollection { { "lastName", SpannerDbType.String, "Garcia" } });

        var singers = new List<Singer>();
        using var reader = await cmd.ExecuteReaderAsync();
        while (await reader.ReadAsync())
        {
            singers.Add(new Singer
            {
                SingerId = reader.GetFieldValue<int>("SingerId"),
                FirstName = reader.GetFieldValue<string>("FirstName"),
                LastName = reader.GetFieldValue<string>("LastName")
            });
        }
        return singers;
    }
}

Go

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 


import (
	"context"
	"fmt"
	"io"

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

func queryWithParameter(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, FirstName, LastName FROM Singers
			WHERE LastName = @lastName`,
		Params: map[string]interface{}{
			"lastName": "Garcia",
		},
	}
	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 int64
		var firstName, lastName string
		if err := row.Columns(&singerID, &firstName, &lastName); err != nil {
			return err
		}
		fmt.Fprintf(w, "%d %s %s\n", singerID, firstName, lastName)
	}
}

Java

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

static void queryWithParameter(DatabaseClient dbClient) {
  Statement statement =
      Statement.newBuilder(
              "SELECT SingerId, FirstName, LastName "
                  + "FROM Singers "
                  + "WHERE LastName = @lastName")
          .bind("lastName")
          .to("Garcia")
          .build();
  try (ResultSet resultSet = dbClient.singleUse().executeQuery(statement)) {
    while (resultSet.next()) {
      System.out.printf(
          "%d %s %s\n",
          resultSet.getLong("SingerId"),
          resultSet.getString("FirstName"),
          resultSet.getString("LastName"));
    }
  }
}

Node.js

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

// 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, FirstName, LastName
        FROM Singers WHERE LastName = @lastName`,
  params: {
    lastName: 'Garcia',
  },
};

// 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}, FirstName: ${json.FirstName}, LastName: ${json.LastName}`
    );
  });
} catch (err) {
  console.error('ERROR:', err);
} finally {
  // Close the database when finished.
  database.close();
}

PHP

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

use Google\Cloud\Spanner\SpannerClient;

/**
 * Queries sample data from the database using SQL with a parameter.
 * Example:
 * ```
 * query_data_with_parameter($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function query_data_with_parameter(string $instanceId, string $databaseId): void
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $results = $database->execute(
        'SELECT SingerId, FirstName, LastName FROM Singers ' .
        'WHERE LastName = @lastName',
        ['parameters' => ['lastName' => 'Garcia']]
    );

    foreach ($results as $row) {
        printf('SingerId: %s, FirstName: %s, LastName: %s' . PHP_EOL,
            $row['SingerId'], $row['FirstName'], $row['LastName']);
    }
}

Python

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

# instance_id = "your-spanner-instance"
# database_id = "your-spanner-db-id"
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, FirstName, LastName FROM Singers "
        "WHERE LastName = @lastName",
        params={"lastName": "Garcia"},
        param_types={"lastName": spanner.param_types.STRING},
    )

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

Ruby

如需了解如何安装和使用 Spanner 客户端库，请参阅 Spanner 客户端库。

如需向 Spanner 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

# 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

sql_query = "SELECT SingerId, FirstName, LastName
             FROM Singers
             WHERE LastName = @lastName"

params      = { lastName: "Garcia" }
param_types = { lastName: :STRING }

client.execute(sql_query, params: params, types: param_types).rows.each do |row|
  puts "#{row[:SingerId]} #{row[:FirstName]} #{row[:LastName]}"
end

后续步骤

如需搜索和过滤其他 Google Cloud 产品的代码示例，请参阅 Google Cloud 示例浏览器。