Jasper grouping not grouping all common dates together - only some

Question

When I group according to date in Jasper, same date entries do not get grouped together.

For example, if I have 3 entries with the same date, two get grouped together, followed by a group of a another date, and then the one that was supposed to get grouped with the other two gets a whole new grouping of it's own later... How do I get the same dates to all group together?

I'm using an oracle database.

Answer 1

To use grouping your data must be sorted firstly by the grouping field i.e. the field you want to group data by must be the first column in your ORDER BY clause as groups are created per occurence of the grouping field. So if the occurrences of the grouping field are not continous you will get multiple groups of the same grouping field.