BigQuery-获取BigQuery表中的列总数

Question

有没有办法查询BigQuery表中的列总数？我浏览了BigQuery文档，但没有找到任何相关内容。

提前致谢！

Answer 1

使用 SQL 查询和内置 INFORMATION_SCHEMA 表：

SELECT count(distinct column_name) 
FROM  `project_id`.name_of_dataset.INFORMATION_SCHEMA.COLUMNS
WHERE table_name = "name_of_table"

Answer 2

有两种方法可以做到这一点：

A.使用BQ命令行工具和JQ linux库解析JSON。

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

这个结果：

4

B.使用REST API进行Tables：get调用

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

这将返回完整的JSON，您可以解析和查询schema.field长度。

{
   "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"
         }
      ]
   }
}