In a demo file I have there's a relationship between two tables between two text fields that should equate to equals but it's not explicitly put as such and doing so breaks the functionality of it.

What they have is "f1 <= f2 AND f1 >= f2", what does this make filemaker do?

Please post the actual relationship and sample data.

I'm referring to the "Type Ahead" portal relation in NightWing's demo (http://www.nightwing.com.au/FileMaker/demosX/demoX03.html)

Basically you have two tables, one table contains the first and last name fields of a contact, and a "search key" field (the format of that field is last name on the first line, then last name space first name on the next line). You then have a "Type ahead" table, with one relational (and the only used) field, "filter", this field is global. Filter's format is on the first line whatever you typed in, on the second line it's whatever you typed in + "zzzz" (the format for an "empty" filter is first line "0" second line "zzzz").

The relation between the "filter" and "search key" is the one described as above:

filter <= search_key AND filter >= search_key

edit: all fields are text types. What I don't get is that because of the AND clause the <= and >= should end up being = because < AND > cancels out.

AND does not cancel out. The relationship filters to show all entries where either the first name or the last name name are alphabetically between the filter. The multikey is carriage-return delimited, and so each value is treated separately and that's how he accomplishes the OR.