SEPARATOR being parsed as a column

[Youssef-Mak]

Given a group_concat invocation:

GROUP_CONCAT([DISTINCT] expr [,expr ...]
  [ORDER BY {unsigned_integer | col_name | expr}
      [ASC | DESC] [,col_name ...]]
  [SEPARATOR str_val])

Select JoinedMonth,
  group_concat(
  distinct FirstName 
  order by FirstName 
  separator '/') as FirstName 
from customers 
group by JoinedMonth

The SEPARATOR keyword will be parsed as a column.