Assign query results to MySQL variable

I'm querying a big mysql database with only read privileges, and I'd like to set some slow query results to a variable, 'foo', so I can use them again in other queries.

Basically, I want to have a variable for a cumbersome subquery, so I can reuse it without having the cost of running it every time I want to use it.

when I enter:

set @foo := (select *
            from table1 join table2 
            where bar = 0 
            group by id);

I get: ERROR 1241 (21000): Operand should contain 1 column(s) and if I restrict to 1 column, ERROR 1242 (21000): Subquery returns more than 1 row

Is there a way to store an array or a table in a variable? I don't have privileges to create temporary tables.