How to use IFNULL() in BigQuery - Standard SQL?

Question

I would like to know how to use the IFNULL() BigQuery Standard SQL function properly. This is my current data structure. The columns named "key" and "stringColumn" store strings. Meanwhile, the column named "integerColumn" stores integers:

I would like to create a new column named "singleValueColumn" that takes the value of the "stringColumn" or "integerColumn" that is not null:

This is my BigQuery Standard SQL query:

SELECT  key,
        value.string_value as stringColumn,
        value.int_value as integerColumn,
        IFNULL(value.string_value, value.int_value) as singleValueColumn

FROM `com_skytracking_ANDROID.app_events_*`, 
      UNNEST(event_dim) as event,
      UNNEST(event.params) as event_param

WHERE event.name = "order_event"

However, when I run the query I am getting this error:

Error: No matching signature for function IFNULL for argument types: STRING, INT64. Supported signature: IFNULL(ANY, ANY) at [4:9]

Thanks for your help.

Solution

Check this doc. I think you need to cast the int_value as a string:

IFNULL(value.string_value, CAST(value.int_value AS STRING)) AS singleValueColumn

Comments

[Milton]

Thanks for your answer. The query is running fine now.