SGBD | File Manager , Buffer Manager | Database library

i'm new in JAVA and Spring boot . i created a spring boot project thene, i created an Entity Class with this code :

I'm trying to create an SQL query from tkinter's checkbutton. The number of criteria of the query depends on the number of checkboxes checked. Here is a first draft of the program :

I have modelized a calendar with a table. The entries are the calendar's events:

id ; event_start_date ; event_end_date.

One entry is:

11 ; 2021-01-28 15:15:37 ; 2022-01-11 15:15:37

The script I've written accepts a search interval of dates as entries and should return all the events which are contained within the search interval (if the search interval is contained in the events intervals, or if one of the search interval dates is contained in the events intervals, or if the events intervals are contained in the search interval). I think that the (unique) case where no results should be returned is: if the search interval is completely out of the bounds of all the events.

Consider the following search interval: search_start_date = 2021-01-26 00:00:00 and search_end_date = 2021-01-30 00:00:00.

Expected behavior: The event #11 should be returned because even though the search_start_date is out of the event's interval, the search_end_date is within it.

Actual behavior: no event is returned.

SGBD used: MySQL. Language used: SQL.

I try to find a way to let the SGBD perform a population of merge fields within a long text.

Create the structure :

My homework requires me to create a single trigger which, under certain circumstances, updates a value AND raises an error. I am using an Oracle database which I access via the sqlplus command on a terminal.

• I cannot use « :NEW.attributeName := value » because raising the error prevents the update.
• I cannot use an update statement inside the trigger because it will raise a mutating table error.
• According to the problem statement I should be able to solve this within a single trigger and the problem statement is kind of vague on this but I think I am not allowed to use a procedure either.
• We have not seen temporary tables in class so they can't be used for the homework. We have however seen views.

For example, let's say I have an sf object containing 4 cities in the contiguous United States and their coordinates. And then I have an sf object with 48 features (one for each possible state). Is there a way to select the subset of states that contain the designated cities? Something like:

Let's say I'm using Oracle SGBD (RDBMS) and Java 8.

I have historical datetimes stored in UTC timezone, but my applications are only displaying local datetimes and my statistical calculations also apply only on local datetimes.

Now, let's say the DST rules change in Europe, as is planned.

What is the easiest way to keep my app and stats working ?

What I've read so far is there are timezones associated with DST rules in both Oracle and Java, but they don't get automatic updates. Moreover, what I'd like to do is to keep the rules before and after the change, not just update the rules since I need historical stats, so I would need "Europe/Paris before change" time zone and "Europe/Paris after change" time zone, or better a timezone associated with a history of rules applying themselves as needed.

Also even if there were some convenient methods to do this in Java, it should still be fixed in Oracle too to cover all the use cases.

Here is one of the relevant historic rule changes in Chicago. DST ends last Sunday of September until 1954, then last Sunday of October from 1955 (until next rule change):

DST Start (Clock Forward) -> DST End (Clock Backward)
1953 dimanche 26 avril, 02 h 00 -> dimanche 27 septembre, 02 h 00
1954 dimanche 25 avril, 02 h 00 -> dimanche 26 septembre, 02 h 00
1955 dimanche 24 avril, 02 h 00 -> dimanche 30 octobre, 02 h 00
1956 dimanche 29 avril, 02 h 00 -> dimanche 28 octobre, 02 h 00

P.S. : I know about IANA historical timezone database, but please show how to practically use it for Oracle SGBD and Java if you have already done so.

P.P.S. : Any advice about what would be better than "UTC" to deal with this issue in future database is also welcome.

Currently I am using SQL Server and having issues, i have a table Adress with 12M of addresses; when i look for one addresses; its take 3 or 4 minutes to find it. i have to look for more than 40000 adressess averyday in my table. so Sql server dont help me to resolve this problem. i think about using an other SGBD maybe MongoDB, but i dont have any idea if it will work or not. my goal is to find every query in less than 2 sec.

My query :

I have 3 tables: droit, role and role_droit. I have many to many relation between droit and role, and role_droit as association table.Please find below the diagram.I would return a matrix like this the diagram below named : Result 2 If we have an intersection between 2 tables droit and role we make 1 else 0. I tried with this query but I got the result in the diagram result 1 :