getting a list of table column names in BigQuery

column_names.sql

// first, grab a list of the field names in a table

SELECT STRING_AGG(column_name, ", \n" ORDER BY ordinal_position)
FROM [project_name].[dataset_name].INFORMATION_SCHEMA.COLUMNS
where table_name = 'blah'
group by table_name

update.sql

// next, select everything again and save it into a new table (or the same table), but recast a field

SELECT 
[field names],
CAST(bad_field AS STRING) AS bad_field, 
[other field names...]
FROM [dataset_name].[table_name]