Manage hours and data in sql query - mysql

Question

I'm planning to study a small webapp in php. I am faced with a problem concerning an SQL query to be performed.
Basically I have to manage reservations based on the date and time. I have separated the two things in a form with a type = date and a type = time.
The date is "data".
The hour is "orario_inizio".
this is my form:
Data: <br><input type="date" name="data" ><br>
Orario Inizio: <br><input type="time" name="orario_inizio" min="09:30:00" max="16:30:00"><br>
Orario Fine: <br><input type="time" name="orario_fine" min="10:00:00" max="18:30:00"><br>
In order for a reservation to be entered in the database it is necessary that "orario_inizio" we have a space of two hours, that is that in the following two hours there are no other bookings.
input.php
// Richiedente
$nominativo = $_POST['nominativo'];
$email = $_POST['email'];
$oggetto = $_POST['oggetto'];
$data = $_POST['data'];
$orario_inizio = $_POST['orario_inizio'];
$orario_fine = $_POST['orario_fine'];
//inserting data order
$query1 = "INSERT INTO Prenotazione (nominativo,email,data,orario_inizio,orario_fine,oggetto,nominativoi,emaili,nominativoe,emaile) VALUES ('$nominativo','$email','$data','$orario_inizio','$orario_fine','$oggetto','$nominativoi','$emaili','$nominativoe','$emaile')"; $result1 = mysqli_query($conn, $query1 );
$result1 = mysqli_query($conn, $query1 );
?>
What I can not understand is how to develop a query that allows me to consider for the date chosen by the user that there are no bookings within two hours. Let me explain with an example:
The user1 wants to make a reservation per day 24 / sept at 10:30 am. I have to make sure that there are no reservations until 12:30. If there are no other bookings already made then I would like to enter this reservation if I send an alert.
I have done the second part, the insert into the database, but i don't have idea how to do about the first check.
$query1 = "INSERT INTO Prenotazione (nominativo,email,data,orario_inizio,orario_fine,oggetto,nominativoi,emaili,nominativoe,emaile) VALUES ('$nominativo','$email','$data','$orario_inizio','$orario_fine','$oggetto','$nominativoi','$emaili','$nominativoe','$emaile')";
I have read that a possibility should be the use of SUBDATE
Can you help me? thank you
UPDATE.
Table Prenotazione
database

Answer 1

Since you provided no table schema, I'll have to use placeholder column names etc.
As explained through comments earlier, you can use the mysql function BETWEEN to see if something is "between" the given times (works for dates also). What it does, is it returns a boolean value. 1 if true, 0 if false.
assuming your table has a date row in order to see the bookings for specific dates, you could write the following example:
$sql="SELECT
COUNT(column_id)
FROM
table_name
WHERE
TIME($orario_inizio) BETWEEN '10:30' AND '12:30'
AND date_column=CURDATE()";
$result_set=mysqli_query($conn, $sql);
$checkIfValid=mysqli_fetch_array($conn, $result_set)[0];
if($checkIfValid > 0) {
//throw error
}
else {
//perform insert query
}
You can tweak the logic to fit your liking a bit better. For instance, CURDATE() just takes the current date, but perhaps you have a specific booking date you can use?
This SQL basically counts an id of your choice (user id or whatnot) based on the condition that the time is between 10:30 AM and 12:30 AM, and that the date is today (could be a given booking date instead).
Now, if this sql finds any records, it will be put into the count. So it either has a value of 0 or higher. If the count is higher than 0, then that means we are busy or however the logic is applied, meaning that you cannot make a booking for that day / time period, and so we throw an error. However, if the count is not bigger than 0, then we proceed with our INSERT, because then everything must be okay.

Answer 2

Consider the following:
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table(booking_id SERIAL PRIMARY KEY,booking_start INT NOT NULL);
INSERT INTO my_table (booking_start) VALUES (3),(7),(10);
SET #n = 9;
INSERT INTO my_table (booking_start)
SELECT #n
FROM (SELECT 1) x
LEFT
JOIN my_table y
ON y.booking_start BETWEEN #n AND #n+2
WHERE y.booking_start IS NULL
LIMIT 1;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
SELECT * FROM my_table;
+------------+---------------+
| booking_id | booking_start |
+------------+---------------+
| 1 | 3 |
| 2 | 7 |
| 3 | 10 |
+------------+---------------+
3 rows in set (0.00 sec)
-- Nothing happens, because 10 is between 9 and 11.
SET #n = 8;
INSERT INTO my_table (booking_start)
SELECT #n
FROM (SELECT 1) x
LEFT
JOIN my_table y
ON y.booking_start BETWEEN #n AND #n+2
WHERE y.booking_start IS NULL
LIMIT 1;
SELECT * FROM my_table;
+------------+---------------+
| booking_id | booking_start |
+------------+---------------+
| 1 | 3 |
| 2 | 7 |
| 3 | 10 |
+------------+---------------+
3 rows in set (0.00 sec)
-- Nothing happens, because 10 is between 8 and 10.
SET #n = 7;
INSERT INTO my_table (booking_start)
SELECT #n
FROM (SELECT 1) x
LEFT
JOIN my_table y
ON y.booking_start BETWEEN #n AND #n+2
WHERE y.booking_start IS NULL
LIMIT 1;
SELECT * FROM my_table;
+------------+---------------+
| booking_id | booking_start |
+------------+---------------+
| 1 | 3 |
| 2 | 7 |
| 3 | 10 |
+------------+---------------+
3 rows in set (0.00 sec)
-- Nothing happens, because 7 is between 7 and 9.
SET #n = 4;
INSERT INTO my_table (booking_start)
SELECT #n
FROM (SELECT 1) x
LEFT
JOIN my_table y
ON y.booking_start BETWEEN #n AND #n+2
WHERE y.booking_start IS NULL
LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM my_table;
+------------+---------------+
| booking_id | booking_start |
+------------+---------------+
| 1 | 3 |
| 2 | 7 |
| 3 | 10 |
| 4 | 4 |
+------------+---------------+
4 rows in set (0.00 sec)
-- Success, because there is no value between 4 and 6.