BigQuery - 使用子查询和OR语句加入多个条件

Question

Is there anyway to join two tables on multiple potential conditions?

I'm currently migrating some code from Postgres to Bigquery where I joined on multiple potential values like:

SELECT
 *
FROM
 (
 SELECT
   offer_table.offer_id
   ,customer_table.customer_name
   ,customer_table.visit_count
   ,ROW_NUMBER() OVER (PARTITION BY offer_table.offer_id ORDER BY customer_table.visit_count DESC) AS customer_visit_rank
 FROM
   offer_table
   LEFT JOIN customer_table ON
    (
    offer_table.customer_id = customer_table.customer_id
    OR offer_table.email = customer_table.email
    OR offer_table.phone = customer_table.phone
    )
 ) dummy
WHERE
  customer_visit_rank = 1

I needed to this because my offer and customer data had inconsistent usage of our id, email, and phone fields but all were valid potential matches. If multiple fields worked (ex: id and email matched), there would be duplicate rows and I'd filter them out based on the row_number column after ranking using the ORDER BY section.

However when I try to join on multiple conditions in BigQuery, I get this error message:

LEFT OUTER JOIN cannot be used without a condition that is an equality of fields from both sides of the join.

Has anyone figured out a solution to join on multiple values instead of doing the above?

Answer 1

You can write separate queries, then use COALESCE :

SELECT
  *
FROM
  (
    SELECT
      offer_table.offer_id
      ,COALESCE(c1.customer_name,c2.customer_name,c3.customer_name)
      ,COALESCE(c1.visit_count,c2.visit_count,c3.visit_count)
      ,ROW_NUMBER() OVER (PARTITION BY offer_table.offer_id ORDER BY customer_table.visit_count DESC) AS customer_visit_rank
    FROM
      offer_table
    LEFT JOIN customer_table c1
      ON offer_table.customer_id = customer_table.customer_id
    LEFT JOIN customer_table c2
      ON offer_table.email = customer_table.email
    LEFT JOIN customer_table c3
      ON offer_table.phone = customer_table.phone
   )
 ) AS dummy
WHERE
  customer_visit_rank = 1