在SQL中使用临时表来更新特定列并输出结果

Question

I have a table in my database which describes a list of different subjects including times the classes are. So the columns in my PostgreSQL database are:

subject_id (type: serial) 
subject (type: character varying)
class start times (type: time without time zone)

When I write my query to list all the subjects I would like to be able to modify the class times for a specific subject. I would like this change to be not permanent but temporary. I understand that I will need to make use of a temporary table in SQL but how can I select everything within my subjects table and make the temporary change of the class times to output to the user. Will I need to first make a temporary subjects tables, use this within my query and then run the UPDATE statement to change the time of a specific class, show this to the user and then DROP the table once it has been done. I understand what needs to be done but I am a little unsure of writing this up in the query.

Answer 1

This question might be clearer if you explained what you were trying to achieve. Why does the start time change for different users?

If you are modifying the start time, for example, to appear in a different time zone, postgres has this ability natively. eg SELECT subject, class_start_time::timestamptz AT TIME ZONE UTC FROM subjects as s ;

If you are trying to add or subtract some arbitrary amount of time, you can do that as well: SELECT subject, class_start_time + interval '1 hour' FROM subjects as s ;