If I understood the last column in Table 1 correctly and it is just a string, you can't.
You cannot write a column into the FORM
-clausal and wait for mysql to evaluate it for every row and find the correct table to join it with.
To do this you will need to create a view where you will have the data from all the tables, together with the table name as an additional column. Afterwards you can perform a join like that between Table1 and the new view