What are you trying to 'Sum'? Sum will add numeric values. What are you trying to do with the = sign? Make Room Type = Sigle? Or see if Room Type is = Single already?
In any formula if you are using a literal string (which I am assuming 'single ' is) you must enclose it in inverted commas: "Single".
Ar you trying to count the number of rooms that are classed as 'Single'?
I"m trying to sum up the number of singles that is in the room type coloum.
There is 3 fields in the rooming type coloum, single, twin and triple.
so i would like to calculate the number of single in that coloum.
hence the sum(roomingtype= single)
Sum doesn't work that way. You might want to look it up in FileMaker help to learn more.
A "column" in filemaker consists of a single field so I'm not sure what you have when you say you have three fields in one column. Do you mean that the field can store the text: "single", "twin" or "triple"?
Do you have a single table here and need to count how many records fall in each category based on which of the above values is entered in a single field?
BTW, the specific error you are getting is because either "single" and/or "roomtype" is not the name of a field in your database.