BigQuery - 获取BigQuery表中的总列数 [英] BigQuery - Get the total number of columns in a BigQuery table

问题描述

有没有办法查询BigQuery表中的列总数？我查阅了BigQuery文档，但没有找到任何相关的内容。

提前致谢！

有几种方法可以做到这一点：

A。使用 BQ 命令行工具以及 JQ linux库来解析JSON。

  bq --format = json show publicdata：samples.shakespeare | jq'.schema.fields |长度'
  

这一点：

<$ p $ B> 4


B。使用REST API执行表格：获取电话

p>

  GET https://www.googleapis.com/bigquery/v2/projects/projectId/datasets/datasetId/tables/tableId 
  

这将返回一个完整的JSON，您可以解析和查询schema.field的长度。

  {
kind：bigquery＃table，
description：这个数据集是，
creationTime：1335916045099，
tableReference：{
projectId：publicdata ，
tableId：shakespeare，
datasetId：samples
}，
numRows：164656，
numBytes ：6432064，
etag：\E7ZNanj79wmDHI9DmeCWoYoUpAE / MTQxMzkyNjgyNzI1Nw\，
lastModifiedTime：1413926827257，
type：TABLE，
id：publicdata：samples。莎士比亚，
selfLink：https://www.googleapis.com/bigquery/v2/projects/publicdata/datasets/samples/tables/shakespeare，
schema：{
字段：[
 {
description：从语料库中提取的一个唯一的单词（其中空格是分隔符）。，
type：STRING ，
name：word，
mode：REQUIRED
}，
 {
description： ，
type：INTEGER，
name：word_count，
mode：REQUIRED
}，
 $ bdescription：从中抽取这个单词的工作，
type：STRING，
name：语料库，
mode：REQUIRED
}，
 {
description：此语料库发布的年份。，
type：INTEGER ，
 name：corpus_date，
mode：必需
} 
] 
} 
} 
  

Is there a way to query the total number of columns in a BigQuery table? I went through the BigQuery documentation but did not find anything relevant.

Thanks in advance!

解决方案

There are a couple of ways to do this:

A. Using the BQ command line tool, and the JQ linux library to parse JSON.

bq --format=json show publicdata:samples.shakespeare | jq '.schema.fields | length'

This outpus:

4

B. Using the REST api to do a Tables:get call

GET https://www.googleapis.com/bigquery/v2/projects/projectId/datasets/datasetId/tables/tableId

this returns a full JSON, that you can parse and query for schema.field length.

{
   "kind":"bigquery#table",
   "description":"This dataset is a word index of the works of Shakespeare, giving the number of times each word appears in each corpus.",
   "creationTime":"1335916045099",
   "tableReference":{
      "projectId":"publicdata",
      "tableId":"shakespeare",
      "datasetId":"samples"
   },
   "numRows":"164656",
   "numBytes":"6432064",
   "etag":"\"E7ZNanj79wmDHI9DmeCWoYoUpAE/MTQxMzkyNjgyNzI1Nw\"",
   "lastModifiedTime":"1413926827257",
   "type":"TABLE",
   "id":"publicdata:samples.shakespeare",
   "selfLink":"https://www.googleapis.com/bigquery/v2/projects/publicdata/datasets/samples/tables/shakespeare",
   "schema":{
      "fields":[
         {
            "description":"A single unique word (where whitespace is the delimiter) extracted from a corpus.",
            "type":"STRING",
            "name":"word",
            "mode":"REQUIRED"
         },
         {
            "description":"The number of times this word appears in this corpus.",
            "type":"INTEGER",
            "name":"word_count",
            "mode":"REQUIRED"
         },
         {
            "description":"The work from which this word was extracted.",
            "type":"STRING",
            "name":"corpus",
            "mode":"REQUIRED"
         },
         {
            "description":"The year in which this corpus was published.",
            "type":"INTEGER",
            "name":"corpus_date",
            "mode":"REQUIRED"
         }
      ]
   }
}

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