title: BigQuery, SQL update command, Error: Scalar subquery produced more than one element
body: <p>I am running the following command: </p>
  
  <pre><code>#standardSQL
    UPDATE `speedy-emissary-167213.pgp_orielresearch.pgp_PIK3CA_all_features_values_step_5` AS t2 
   SET 
    chr3_3308581_TGGGGT=IF(t1.PIK3CA_features="chr3_3308581_TGGGGT",1,0),
    chr3_3294651_CA=IF(t1.PIK3CA_features="chr3_3294651_CA",1,0),
    chr3_3300867_CC=IF(t1.PIK3CA_features="chr3_3300867_CC",1,0),
    chr3_3308373_ACTTGACTTG=IF(t1.PIK3CA_features="chr3_3308373_ACTTGACTTG",1,0),
    chr3_3309125__T=IF(t1.PIK3CA_features="chr3_3309125__T",1,0),
  ......
    chr3_3300985_TT=IF(t1.PIK3CA_features="chr3_3300985_TT",1,0),
    chr3_3308139_AC=IF(t1.PIK3CA_features="chr3_3308139_AC",1,0)
  FROM
    `speedy-emissary-167213.pgp_orielresearch.pgp_PIK3CA_all_features_values_step_4_sorted_500` AS t1
  WHERE
    t1.sample_id = t2.sample_id
  </code></pre>
  
  <p>When i run it with 500 "chr3_3308581_TGGGGT=IF(t1.PIK3CA_features="chr3_3308581_TGGGGT",1,0),"  for different columns, the Scalar subquery produced more than one element is fired. when i run it with less command (by deleting part of it), the command runs successfully. what would be the easiest way to debug this query?</p>
  
  <p>Thanks!</p>