title: Can bigquery query flattern tables and convert it into nest data structure
body: <p>Now I'm facing a problem that there are 5 tables in bigquery,
  image that table A have a record that in table B there are 5 records have some connections with it .Here is the example:
  Table A: record a
  Table B: record b,c,d,e,f</p>
  
  <p>Now I'm using this sql:</p>
  
  <pre><code>select A.*,B.* from A join each B on A.xx = B.xx
  </code></pre>
  
  <p>and the query results like this:<code>a,b;a,c;a,d;a,e;a,f;</code>(show in 5 rows)</p>
  
  <p>is there any idea to make the result like this:</p>
  
  <pre><code>a,b c d e f; (show in 1 row)
  </code></pre>
  
  <p>Hope your help!
  thanks!</p>