How to concatenate strings of a string field in a PostgreSQL 'group by' query?

Question

I am looking for a way to concatenate the strings of a field within a group by query. So for example, I have a table:

ID   COMPANY_ID   EMPLOYEE
1    1               


        

Answer 1

Use STRING_AGG function for PostgreSQL and Google BigQuery SQL:

SELECT company_id, STRING_AGG(employee, ', ')
FROM employees
GROUP BY company_id;