使用条件更新 BigQuery 重复记录字段

Question

I have a BigQuery table named 'events' with below structure:

Data example:

My goal is to update all rows where country is US and replace it with 'United States', and where country is CH to replace it with 'China'.

I tried to look at other questions where they update repeated record but I didn't find anything specific to what I want and didn't quite understood the method. (for example this StackOverflow question )

Any help would be much appreciated.

Answer 1

If you're trying to modify only two country codes into country names, following would be one of possible approach.

Note - below query is assuming that country code and region code can conflict each other.

UPDATE sample
   SET attributes = ARRAY (
     SELECT AS STRUCT a.name, IFNULL(c.name, a.value)
       FROM UNNEST(attributes) a 
       LEFT JOIN UNNEST([
         STRUCT('US' AS code, 'United States' AS name), ('CH', 'China')
       ]) c ON a = ('country', c.code)
   )
 WHERE ('country', 'US') IN UNNEST(attributes)
    OR ('country', 'CH') IN UNNEST(attributes)
;

More general approach would be using a mapping table.

DECLARE countries ARRAY<STRUCT<code STRING, name STRING>> DEFAULT [
  ('US', 'United States'),
  ('CH', 'China') --, you can add more mappings of country code and it's name.
];

With the above mapping table, below query will generate same result as first query.

UPDATE sample
   SET attributes = ARRAY(
     SELECT AS STRUCT a.name, IFNULL(c.name, a.value)
       FROM UNNEST(attributes) a 
       LEFT JOIN UNNEST(countries) c ON a = ('country', c.code)
   )
 WHERE TRUE
;