I have 5 datasets to recored the temperature and humidity at 5 different locations, and each location record it once an hour but different timing. e.g. Site-A records it at every quarter to the hour, Site-B records it at half past every hour. I appended those into 1 query. and draw the line chart and got following. Up to 15:00, there are only outside temperature so I see the line, but after that no lines show up and only dots. But I like each dataset continues smoothly, and like to see only lines in different colors to compare those.