The limitation isn't within Fabrik or our elements table, it's a built in limitation of 65535 byte "row size" on tables in MySQL. Each column has a size. So a VARCHAR(255) is 255 bytes, or 765 if your database is UTF-8 (where each character is 3 bytes). An INTEGER is 4 bytes. Etc. And that combined size cannot exceed 65535 bytes (64kb).
So the data tables you create within Fabrik have MySQL imposed limitations on how many columns of what size they can have. By default, we create our simple 'field' elements as VARCHAR(255). So the maximum would be 257 (well, minus a little for the PK 'id' element), or 85 if you are using UTF-8 encoding. To squeeze 700 simple VARCHAR columns in, the average size would have to be about 93 characters (or 31 if UTF-8).
You can reduce the size of field elements, by specifying the length ("Max Length" in the Advanced tab). We'll then change the VARCHAR size of the underlying column. What size you can set it to obviously depends on your data.
Or you could probably manually change those columns in the underlying table to "TEXT" instead of VARCHAR, as those don't take up space the way VARCHAR does, although that could impose other performance and functionality issues. TEXT data is stored "off table", whereby the data in the actual table row within the database is a pointer to another area of storage, so the database engine has to make an extra file system call for each TEXT column it is loading.
HOWEVER ... even if you manage to create a MySQL table with 700 columns, it's going to be extremely slow to actually use in Fabrik. I can't give hard metrics, as it depends entirely on what mix of element types you have, and whether you can exclude a lot of the elements from the list querying, etc. But typically we recommend keeping the number of elements under 100. We have some clients who have pushed that into the 200s, or even 300 or more. But I doubt very much 700 is a workable number.
-- hugh
