https://github.com/fadilxcoder/sql-query
SQL query explained
https://github.com/fadilxcoder/sql-query
notes php poc sql
Last synced: 9 months ago
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SQL query explained
- Host: GitHub
- URL: https://github.com/fadilxcoder/sql-query
- Owner: fadilxcoder
- Created: 2021-03-20T18:33:35.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2022-08-18T17:28:00.000Z (over 3 years ago)
- Last Synced: 2025-02-23T09:14:44.848Z (about 1 year ago)
- Topics: notes, php, poc, sql
- Language: PHP
- Homepage:
- Size: 57.6 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# NOTES
## DB
- *users* 1 - N *cards*
- *users* 1 - N *addresses*
- Update table with random integer : `UPDATE tbl_name SET column_name = CAST(RAND() * 10000 AS UNSIGNED)`
## JOINS
### Information
- FULL JOIN === FULL OUTER JOIN *Does not work in MySQL*
- LEFT OUTER JOIN === LEFT JOIN
- RIGHT OUTER JOIN === RIGHT JOIN
- INNER JOIN === JOIN
**Above illustration A is` users`, B is `cards`**
> SELECT U.id, U.fname, U.lname, C.type, C.amount
FROM `users` AS U
INNER JOIN `cards` AS C
WHERE C.uid = U.id
*Return only matched - 300,000 results*
> SELECT U.id, U.fname, U.lname, C.type, C.amount
FROM `users` AS U
LEFT JOIN `cards` AS C
ON C.uid = U.id
*Return matched & all in users - 2,969,158 results*
> SELECT U.id, U.fname, U.lname, C.type, C.amount
FROM `users` AS U
RIGHT JOIN `cards` AS C
ON C.uid = U.id
*Return matched & all in cards - 300,000 results*
> SELECT *
FROM users
CROSS JOIN cards
*Return combinations of each row of users < first_table > with **all** records in cards < second_table > - 886,334,700,000 results*
## HAVING / GROUP BY / UNION
### Reference
- The GROUP BY statement is often used with aggregate functions (COUNT(), MAX(), MIN(), SUM(), AVG()) to group the result-set by one or more columns.
- https://www.w3schools.com/sql/sql_groupby.asp
> SELECT U.id, U.fname, U.lname, C.amount
FROM `users` AS U
INNER JOIN `cards` AS C
ON C.uid = U.id
HAVING U.id < 100
*Return only matched & all user.id < 100 - 14 results*
> SELECT sum(amount), type
FROM cards
GROUP BY type
ORDER BY type ASC
*Return 5 type of card with sum of amount per card type - 5 results*
> SELECT concat('C', C.id) AS id, C.uid, 'Cards' AS status
FROM cards AS C
UNION
SELECT concat('A', A.id) AS id, A.uid, 'Addresses' AS status
FROM addresses AS A
*Return all of cards & all of addresses, **note that columns need to be of the same type** - 598,862 results*
## VIEW
> CREATE VIEW view_1 AS
SELECT U.id, U.fname, U.lname, C.amount
FROM `users` AS U
INNER JOIN `cards` AS C
ON C.uid = U.id
HAVING U.id < 100
*Will create view_1 in phpMyAdmin listed under Structure with type:**View***
---
# Additional Notes
- https://dev.mysql.com/doc/refman/8.0/en/json-creation-functions.html ( Functions That Create JSON Values)
```sql
SELECT
vip_list.id AS id,
vip_list.name AS name,
vip_list.surname AS surname,
JSON_OBJECT(
'qa', vip_list.qa,
'status', vip_list.status,
'net_worth', vip_list.net_worth,
'registered_at', vip_list.registered_at
) AS details
from vip_list
```