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I am building a Hamper website for a local church for their Christmas hamper drive, and I am looking for some guidance on how to achieve the desired MySQL query / result. The intended page is just a client index, but it shows the current / active hamper_no ( C(ouple)001 ), name, address, phone number,... And In order to have the correct information, I wrote a query, first SELECT ... FROMclients as c JOINhampers as h ON ... To keep it simple, the (first)clients table looks like this:
| id | hamper_id (index) DEFAULT NULL | name |
|---|---|---|
| 1 | 2 | DOE, John |
| 2 | null | DOE, Jane |
| 3 | null | DOE, Jack |
Based on https://stackoverflow.com/a/2111420/3095210
This is an example of the greatest-n-per-group problem that has appeared regularly on StackOverflow.
SELECT h1.`id` AS h_id,
h1.`client_id` AS c_id,
IF(YEAR(h1.`created_date`) = 2022, h1.`hamper_no`, NULL) AS hamper_no,
YEAR(h1.`created_date`) AS h_year,
c.`id`,
`hamper_id`,
`name`
FROM `clients` AS c
LEFT JOIN `hampers` AS h1
ON c.`id` = h1.`client_id`
LEFT OUTER JOIN `hampers` AS h2
ON (
c.id = h2.client_id
AND
(
h1.created_date < h2.created_date
OR
(
h1.created_date = h2.created_date
AND h1.id < h2.id
)
)
)
WHERE h2.id IS NULL
ORDER BY `name`;
| h_id | c_id | hamper_no | h_year | id | hamper_id | name |
|---|---|---|---|---|---|---|
| null | null | null | null | 3 | null | DOE, Jack |
| 3 | 2 | F001 | 2022 | 2 | null | "DOE, Jane" |
| 2 | 1 | C012 | 2022 | 1 | 2 | "DOE, John" |
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PHP (from the English Hypertext Preprocessor - hypertext preprocessor) is a scripting programming language for developing web applications. Supported by most hosting providers, it is one of the most popular tools for creating dynamic websites.
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DBMS is a database management system. It is designed to change, search, add and delete information in the database. There are many DBMSs designed for similar purposes with different features. One of the most popular is MySQL.
It is a software tool designed to work with relational SQL databases. It is easy to learn even for site owners who are not professional programmers or administrators. MySQL DBMS also allows you to export and import data, which is convenient when moving large amounts of information.
https://www.mysql.com/
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