BigQuery supports the following format for commenting code. The following is an example of single-line commenting, where anything from the start, to the end of that line is ignored when executing the query:

#legacySQL
SELECT 
      repo_name, --repository name
      language.name --programming language
FROM [bigquery-public-data:github_repos.languages] 

A multi-line comment is specified by enclosing the text within /* */, as shown in this query:

#legacySQL
/*
This query will return the repository name 
and the programming languages used in the repository.
*/
SELECT 
      repo_name, --repository name
      language.name --programming language
FROM [bigquery-public-data:github_repos.languages] 

The SQL language includes about 10 main commands; however, the SELECT command is the command used to extract data from tables. This command is used with five other general statements or clauses to run most queries.