How to select specifc entries in MySQL/PHP - php

Question

I'm dealing with this problem. There is tableorders(oid,datetime,quantity,title,username,mid).
The table orders is updated from php code as far as the features oid,datetime,quantity,title,username are concerned. The problem is that I want to classify each entry based on both datetime and username so as to gather these entries under an order code in order to make an ordering entry. (I can't think of anything else at the moment).
The question is how can I select those entries that are corresponding to the same username and the same date time.
For example the if I have 3entries (freddo espresso,latte,freddoccino) belong to the same order procedure (are posted by the same username, tha exact same datetime) and I need to present them to my user as a completed order.
Here is the structure of table orders:
CREATE TABLE IF NOT EXISTS `orders` (
`oid` INT UNSIGNED NOT NULL AUTO_INCREMENT,
`datetime` DATETIME NOT NULL,
`quantity` INT NOT NULL,
`sum` FLOAT(4,2) NOT NULL,
`title` VARCHAR(30) COLLATE utf8_unicode_ci NOT NULL,
`username` VARCHAR(30) COLLATE utf8_unicode_ci NOT NULL,
`mid` VARCHAR(30) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`oid`),
KEY `username`(`username`,`mid`,`title`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=10000;
The feature title is foreign key from table products:
CREATE TABLE IF NOT EXISTS `products`(
`title` VARCHAR(30) COLLATE utf8_unicode_ci NOT NULL,
`descr` TEXT(255),
`price` FLOAT(4,2) NOT NULL,
`popularity` INT NOT NULL,
`cname` VARCHAR(20) COLLATE utf8_unicode_ci NOT NULL,
`mid` VARCHAR(30) COLLATE utf8_unicode_ci NOT NULL ,
PRIMARY KEY(`title`),
KEY `cname` (`cname`, `mid`)
)ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=10000;
Sorry If I'm a little uncomprehensive, though I really need some help to come to a conclusion. Any ideas?
Thanks in advance!

Answer 1

If you know what the datetime value and the username values are then you can simply use:
SELECT * FROM orders WHERE username = '$username' AND datetime = '$datetime'
However, what you would be better off doing is splitting this into two separate tables; something like:
Orders
OrderID
OrderTime
UserName
Items
ItemID
OrderID
Title
Then you would search in the following way:
SELECT Orders.OrderID, Orders.UserName, Items.Title
FROM Orders
INNER JOIN Items ON Orders.OrderID = Items.OrderID
WHERE
Orders.UserName = '$username'
AND
Orders.OrderDate = '$datetime'
When adding orders you add a record to Orders first, and then use that OrderID and add it to each item inserted in Items...
Insert Example
$mysqli; //Assuming your connection to the database...
$items; //Assuming an array of items for the order like: array('Coffee', 'Tea')
$username; //Assuming the user name to be inserted for the order
$mysqli->query("INSERT INTO Orders(`OrderTime`, `UserName`) VALUES(NOW(), '$username')");
$orderid = $mysqli->insert_id;
foreach($items as $item){
$mysqli->query("INSERT INTO Items (`OrderID`, `Title`) VALUES($orderid, '$title')");
}
NOTE: You should make sure to sanitize data before inserting to database...
Storing JSON
Storing JSON in a database is going to require you to make sure that you use a field data type that is an appropriate length (e.g. a blob).
You mentioned that you retrieve the titles as an array from a form so I'm now going to refer to that as $titles.
Saving to database
$username = '...'; // Username or id to store in database with order
$titles = array(.....); // Array of titles from form
$encodedTitles = json_encode($titles); // Convert to JSON
$mysqli->query("INSERT INTO table_name (titles_field, username_field, date_field) VALUES ('$titles', '$username', NOW())"); // Save to database (assuming already open connection
Retrieve from database
$result = $mysqli->query("SELECT titles FROM table_name WHERE username = 'username_value' AND date_field = 'date_value'"); //Run query to get row
$row = $result->fetch_assoc(); // Fetch row
$titles = json_decode($row['titles']); // This is the same as the `titles` array from the from above!

Answer 2

SELECT quantity,title
FROM orders
WHERE username = ? and datetime = ?
Would return the quantity of items for a specific user on specific date. Instead of a date you could use an order id, which might be a bit safer. If you use order id, then username becomes irrelevant as well, since order ids should be unique.

Answer 3

The answer posted with the query will help you but you should also consider changing your table structure. Looks like you could have a table named orders and another one named orders_items. Then you could list all the itens from orders_itens matching a single order.

Answer 4

I think this query will return kind of data where you have the same unique_id string for records where username and datetime are the same.
SELECT MD5(a.unique_id), b.* FROM (
SELECT
GROUP_CONCAT(oid) unique_id, `datetime`, username
FROM `orders` GROUP BY username, `datetime`
) a
RIGHT JOIN `orders` b
ON a.`datetime` = b.`datetime` AND a.username = b.username
ORDER BY unique_id, oid;
I also have another answer for about 3 thousands characters long but I think this variant will help you more than my long tutorial how to split the table to two tables and how to migrate data into it + php code samples. So I decided not publicate it. )))
Edit: I think you even can run this one query which is easiest and works faster:
SELECT *, MD5( CONCAT( `username` , `datetime` ) ) unique_id
FROM `orders`
ORDER BY unique_id, oid;