title: CROSS JOIN more than two tables
body: <p>I have three tables, t1, t2 and t3. Table structure and values:</p>
  
  <pre><code>t1_id | t1_k1 | t1_val
  ------+-------+--------
  1     | k1foo | t1foo
  2     | k1bar | t1bar
  3     | k1baz | t1baz
  
  t2_id | t2_k1 | t2_k2 | t2_val
  ------+-------+-------+--------
  1     | k1foo | k2foo | t2foo
  2     | k1bar | k2bar | t2bar
  3     | k1baz | k2baz | t2baz
  
  t3_id | t3_k2 | t3_val
  ------+-------+--------
  1     | k2foo | t3foo
  2     | k2bar | t3bar
  3     | k2baz | t3baz
  </code></pre>
  
  <p>So with normal SQL I can join t1 and t2 on t1_k1 = t2_k1 and t2 and t3 on t2_k2 = t3_k2, that is:</p>
  
  <pre><code>SELECT t1_val, t2_val, t3_val
  FROM t1, t2, t3
  WHERE t1_k1 = t2_k1 AND t2_k2 = t3_k2
  </code></pre>
  
  <p>To get</p>
  
  <pre><code>t1foo | t2foo | t3foo
  t1bar | t2bar | t3bar
  t1baz | t2baz | t3baz
  </code></pre>
  
  <p>Now I'm trying to get the same result with bigQuery SQL. From my understanding, using CROSS JOIN should work just like the comma in regular SQL, so I thought the following would work:</p>
  
  <pre><code>SELECT t1_val, t2_val, t3_val
  FROM test.t1 CROSS JOIN test.t2 CROSS JOIN test.t3
  WHERE t1_k1 = t2_k1 AND t2_k2 = t3_k2
  </code></pre>
  
  <p>But I get an error that "Field 't3_k2' not found on either side of the JOIN".
  Adding parentheses like this:</p>
  
  <pre><code>SELECT SELECT t1_val, t2_val, t3_val
  FROM ((test.t1 CROSS JOIN test.t2) CROSS JOIN test.t3)
  WHERE t1_k1 = t2_k1 AND t2_k2 = t3_k2
  </code></pre>
  
  <p>gives a (frankly quite cryptic) syntax error 'Encountered "" at line 0, column 0.'
  With just two tables CROSS JOIN works, but then it's no different from a normal JOIN.
  I haven't found examples using CROSS JOIN on more than two tables. Is it possible? Am I doing something wrong?</p>