If the sum() functions doesn't find any matches it returns an empty string. I suggest it would be better to return zero. Otherwise you can get a fatal error if you try to use the result in a function that will not accept a string.
The documentation at https://medoo.in/api/sum says that the return will be a number.
I haven't tested, but the same may be true for the other Aggregation functions.
If the sum() functions doesn't find any matches it returns an empty string. I suggest it would be better to return zero. Otherwise you can get a fatal error if you try to use the result in a function that will not accept a string.
The documentation at https://medoo.in/api/sum says that the return will be a number. I haven't tested, but the same may be true for the other Aggregation functions.