Mengubah kolom dalam tugas penambahan kueri

Mengubah kolom dari wajib menjadi nullable dalam tugas penambahan kueri.

Jelajahi lebih lanjut

Untuk melihat dokumentasi mendetail yang menyertakan contoh kode ini, lihat referensi berikut:

• Mengubah skema tabel

Contoh kode

Go

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Go di Panduan memulai BigQuery menggunakan library klien. Untuk mengetahui informasi selengkapnya, lihat Dokumentasi referensi BigQuery Go API.

Untuk melakukan autentikasi ke BigQuery, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, lihat Menyiapkan autentikasi untuk library klien.

import (
	"context"
	"fmt"

	"cloud.google.com/go/bigquery"
)

// relaxTableQuery demonstrates relaxing the schema of a table by appending query results to
// enable the table to allow NULL values.
func relaxTableQuery(projectID, datasetID, tableID string) error {
	// projectID := "my-project-id"
	// datasetID := "mydataset"
	// tableID := "mytable"
	ctx := context.Background()
	client, err := bigquery.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("bigquery.NewClient: %w", err)
	}
	defer client.Close()

	sampleSchema := bigquery.Schema{
		{Name: "full_name", Type: bigquery.StringFieldType, Required: true},
		{Name: "age", Type: bigquery.IntegerFieldType, Required: true},
	}
	meta := &bigquery.TableMetadata{
		Schema: sampleSchema,
	}
	tableRef := client.Dataset(datasetID).Table(tableID)
	if err := tableRef.Create(ctx, meta); err != nil {
		return err
	}
	// Now, append a query result that includes nulls, but allow the job to relax
	// all required columns.
	q := client.Query("SELECT \"Beyonce\" as full_name")
	q.QueryConfig.Dst = client.Dataset(datasetID).Table(tableID)
	q.SchemaUpdateOptions = []string{"ALLOW_FIELD_RELAXATION"}
	q.WriteDisposition = bigquery.WriteAppend
	q.Location = "US"
	job, err := q.Run(ctx)
	if err != nil {
		return err
	}
	_, err = job.Wait(ctx)
	if err != nil {
		return err
	}
	return nil
}

Java

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Java di Panduan memulai BigQuery menggunakan library klien. Untuk mengetahui informasi selengkapnya, lihat Dokumentasi referensi BigQuery Java API.

Untuk melakukan autentikasi ke BigQuery, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, lihat Menyiapkan autentikasi untuk library klien.

import com.google.cloud.bigquery.BigQuery;
import com.google.cloud.bigquery.BigQueryException;
import com.google.cloud.bigquery.BigQueryOptions;
import com.google.cloud.bigquery.Job;
import com.google.cloud.bigquery.JobInfo;
import com.google.cloud.bigquery.JobInfo.SchemaUpdateOption;
import com.google.cloud.bigquery.JobInfo.WriteDisposition;
import com.google.cloud.bigquery.QueryJobConfiguration;
import com.google.cloud.bigquery.TableId;
import com.google.cloud.bigquery.TableResult;
import com.google.common.collect.ImmutableList;

public class RelaxTableQuery {

  public static void main(String[] args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "MY_PROJECT_ID";
    String datasetName = "MY_DATASET_NAME";
    String tableName = "MY_TABLE_NAME";
    relaxTableQuery(projectId, datasetName, tableName);
  }

  // To relax all columns in a destination table when you append data to it during a query job
  public static void relaxTableQuery(String projectId, String datasetName, String tableName)
      throws Exception {
    try {
      // Initialize client that will be used to send requests. This client only needs to be created
      // once, and can be reused for multiple requests.
      BigQuery bigquery = BigQueryOptions.getDefaultInstance().getService();

      TableId tableId = TableId.of(datasetName, tableName);

      String sourceTable = "`" + projectId + "." + datasetName + "." + tableName + "`";
      String query = "SELECT word FROM " + sourceTable + " WHERE word like '%is%'";

      QueryJobConfiguration queryConfig =
          QueryJobConfiguration.newBuilder(query)
              // Use standard SQL syntax for queries.
              // See: https://cloud.google.com/bigquery/sql-reference/
              .setUseLegacySql(false)
              .setSchemaUpdateOptions(ImmutableList.of(SchemaUpdateOption.ALLOW_FIELD_RELAXATION))
              .setWriteDisposition(WriteDisposition.WRITE_APPEND)
              .setDestinationTable(tableId)
              .build();

      Job queryJob = bigquery.create(JobInfo.newBuilder(queryConfig).build());

      queryJob = queryJob.waitFor();

      // Check for errors
      if (queryJob == null) {
        throw new Exception("Job no longer exists");
      } else if (queryJob.getStatus().getError() != null) {
        // You can also look at queryJob.getStatus().getExecutionErrors() for all
        // errors, not just the latest one.
        throw new Exception(queryJob.getStatus().getError().toString());
      }

      // Get the results.
      TableResult results = queryJob.getQueryResults();

      // Print all pages of the results.
      results
          .iterateAll()
          .forEach(
              rows -> {
                rows.forEach(row -> System.out.println("row: " + row.toString()));
              });

      System.out.println("Successfully relaxed all columns in destination table during query job");
    } catch (BigQueryException | InterruptedException e) {
      System.out.println("Columns not relaxed during query job \n" + e.toString());
    }
  }
}

Node.js

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Node.js di Panduan memulai BigQuery menggunakan library klien. Untuk mengetahui informasi selengkapnya, lihat Dokumentasi referensi BigQuery Node.js API.

Untuk melakukan autentikasi ke BigQuery, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, lihat Menyiapkan autentikasi untuk library klien.

const {BigQuery} = require('@google-cloud/bigquery');
const bigquery = new BigQuery();

async function relaxColumnQueryAppend() {
  // Change required to null in query append job

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = "my_project"
  // const datasetId = "my_dataset"
  // const tableId = "my_table"

  // Retrieve the destination table and checks the number of required fields.
  const dataset = await bigquery.dataset(datasetId);
  const table = await dataset.table(tableId);
  const [metaData] = await table.getMetadata();

  const requiredFields = metaData.schema.fields.filter(
    ({mode}) => mode === 'REQUIRED'
  ).length;

  console.log(`${requiredFields} fields in the schema are required.`);

  // Create destination table reference
  const tableRef = {
    projectId,
    tableId,
    datasetId,
  };

  /* Configure the query to append the results to a destination table,
   * allowing field relaxation. In this example, the existing table
   * contains 'age' as a required column.
   *
   * For all options, see https://cloud.google.com/bigquery/docs/reference/rest/v2/Job#JobConfigurationQuery
   */
  const queryJobConfig = {
    query: `SELECT age FROM \`${projectId}.${datasetId}.${tableId}\``,
    destinationTable: tableRef,
    schemaUpdateOptions: ['ALLOW_FIELD_RELAXATION'],
    writeDisposition: ['WRITE_APPEND'],
    useLegacySql: false,
  };

  // Configure the job.
  const jobConfig = {
    configuration: {
      query: queryJobConfig,
    },
  };

  // Start the query, passing in the extra configuration.
  const response = await bigquery.createJob(jobConfig);
  const job = response[0];

  // Wait for job to complete.
  await job.getQueryResults(job);

  // Check the updated number of required fields.
  const updatedTable = await dataset.table(tableId);
  const [updatedMetaData] = await updatedTable.getMetadata();

  const updatedRequiredFields = updatedMetaData.schema.fields.filter(
    ({mode}) => mode === 'REQUIRED'
  ).length;

  console.log(
    `${updatedRequiredFields} fields in the schema are now required.`
  );
}

Python

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Python di Panduan memulai BigQuery menggunakan library klien. Untuk mengetahui informasi selengkapnya, lihat Dokumentasi referensi BigQuery Python API.

Untuk melakukan autentikasi ke BigQuery, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, lihat Menyiapkan autentikasi untuk library klien.

from google.cloud import bigquery

# Construct a BigQuery client object.
client = bigquery.Client()

# TODO(developer): Set table_id to the ID of the destination table.
# table_id = "your-project.your_dataset.your_table_name"

# Retrieves the destination table and checks the number of required fields.
table = client.get_table(table_id)  # Make an API request.
original_required_fields = sum(field.mode == "REQUIRED" for field in table.schema)

# In this example, the existing table has 2 required fields.
print("{} fields in the schema are required.".format(original_required_fields))

# Configures the query to append the results to a destination table,
# allowing field relaxation.
job_config = bigquery.QueryJobConfig(
    destination=table_id,
    schema_update_options=[bigquery.SchemaUpdateOption.ALLOW_FIELD_RELAXATION],
    write_disposition=bigquery.WriteDisposition.WRITE_APPEND,
)

# Start the query, passing in the extra configuration.
client.query_and_wait(
    # In this example, the existing table contains 'full_name' and 'age' as
    # required columns, but the query results will omit the second column.
    'SELECT "Beyonce" as full_name;',
    job_config=job_config,
)  # Make an API request and wait for job to complete

# Checks the updated number of required fields.
table = client.get_table(table_id)  # Make an API request.
current_required_fields = sum(field.mode == "REQUIRED" for field in table.schema)
print("{} fields in the schema are now required.".format(current_required_fields))

Langkah selanjutnya

Untuk menelusuri dan memfilter contoh kode untuk produk Google Cloud lainnya, lihat browser contoh Google Cloud.