I have an uptodate debian stable installation. I have a mysql database containing a single table. This table has a few cols, like date, total (non-null) and also some others.
I opened libreoffice calc, created a pivot table using odbc to connect to that mysql database and retrieve those data from my table. Only those two columns were taken (I wanted to draw a chart), but some values were missing (= there were a few empty cells in the column A). I have modified the pivot table using other data but the fist col contained some empty cells again.

Do you know is this a bug or am I missed something?

Finally I imported a third column too, that was not used in my graph.