How to fill in missing records in a MySQL selection grouped by day/hour?

Question

MySQL

There is a table, statistics on user transitions are written to it.
It has a timestamp field.
I make a selection by the number of records for a certain hour / day and group by this hour / day, but if there was no transition at a certain hour / day, then accordingly this record will not fall into the selection and will not be displayed on the chart.
How to fill in these missing entries so that everything is consistent?

Answer 1

The easiest way is to prepare a TEMPORARY table with a timestamp and substitute the values ​​with your table via LEFT JOIN.

Answer 2

stackoverflow.com/questions/24305085/including-mis...
stackoverflow.com/questions/10429611/mysql-group-b...